阅读说明：本技术 一种纳米cBN-hBN复合共沉积增强金属基梯度镀层制备方法 (Preparation method of nano cBN-hBN composite codeposition enhanced metal-based gradient coating ) 是由 王东生 屈光 汪群友 华盟章 于 2021-06-09 设计创作，主要内容包括：本发明涉及电沉积技术领域,具体的说是一种纳米cBN-hBN复合共沉积增强金属基梯度镀层制备方法,包括对基体表面进行预处理；以立方结构和六方结构同素异构体为增强相,以金属为电镀层母相,电镀时使增强相在镀液中含量逐渐增加呈梯度变化,形成颗粒增强金属基梯度复合镀层；对镀层进行电接触强化。基于立方结构增强相的高硬度和六方结构增强相的层状滑移性；通过纳米增强相及其梯度分布的集同效应,大大提高金属基复合镀层的性能；通过对镀层进行电接触强化,不仅改善镀层表面以及内部的质量,而且使镀层与基体之间的结合从机械结合转变为冶金结合,极大提高了镀层与基体之间结合力。(The invention relates to the technical field of electrodeposition, in particular to a preparation method of a nanometer cBN-hBN composite codeposition enhanced metal-based gradient coating, which comprises the steps of pretreating the surface of a substrate; cubic structure and hexagonal structure isomer are taken as reinforced phases, metal is taken as a mother phase of an electroplated layer, and the content of the reinforced phases in the electroplating solution is gradually increased and is changed in a gradient manner during electroplating to form a particle reinforced metal-based gradient composite coating; and carrying out electric contact strengthening on the plating layer. Based on the high hardness of the cubic structure reinforcing phase and the lamellar slippage of the hexagonal structure reinforcing phase; the performance of the metal-based composite coating is greatly improved through the integration effect of the nanometer reinforcing phase and the gradient distribution thereof; by strengthening the electric contact of the plating layer, the quality of the surface and the interior of the plating layer is improved, the bonding between the plating layer and the substrate is changed from mechanical bonding to metallurgical bonding, and the bonding force between the plating layer and the substrate is greatly improved.)

1. A preparation method of a nanometer cBN-hBN composite codeposition reinforced metal-based gradient coating is characterized by comprising the following steps:

step S1: pretreating the surface of the substrate;

step S2: on the surface of the matrix processed in the step S1, cubic structure and hexagonal structure isomorphism isomers are used as a reinforcing phase, metal is used as a mother phase of an electroplated layer, and the content of the reinforcing phase in the electroplating solution is gradually increased and is changed in a gradient manner during electroplating to form a particle reinforced metal-based gradient composite plated layer;

step S3: putting the plating layer obtained in the step S2 in an electric contact strengthening device for electric contact strengthening, wherein;

the electrode (38) is tightly pressed on the surface of a workpiece under the drive of the cylinder (31), the pressure between the electrode (38) and the workpiece is controlled to be 98N, the electrode (38) rotates in the reverse direction due to friction force, the electrode (38) rotates while making feed motion on the surface of a sample, and when the electrode (38) makes feed motion, large current is conducted, and resistance heat with high energy density is generated on the surface of the workpiece by the current to quench and strengthen the surface of a coating.

2. The method as claimed in claim 1, wherein the pretreatment in step S1 comprises sanding, degreasing, and activating with weak acid, and the surface of the substrate is washed with deionized water between each step.

3. The method as claimed in claim 1, wherein the reinforcing phase in step S2 is one of diamond-graphite and cBN-hBN, and the grain size of the reinforcing phase is 10-80 nm.

4. The method as claimed in claim 1, wherein the matrix phase of the metal-based plating layer in step S2 is one of Ni, Ni-P, Ni-W, Ni-Co, Ni-Fe, Ni-Mo, Ni-Mn, Ni-Co-Mn, and Ni-Fe-P.

5. The method as claimed in claim 1, wherein the pressure between the electrode and the workpiece is 49-196N, the feeding speed of the electrode is 0.5-2 mm/min, and the current is 30-50 kA during the electrical contact strengthening in step S3.

6. The method for preparing a nano composite codeposition enhanced metal-based gradient coating according to claim 1, wherein the electrical contact strengthening device in the step S3 comprises a housing (1), a support plate (11) is fixed on the top of the housing (1), a through slot matched with the clamping mechanism (2) is formed in the middle of the support plate (11), a servo motor (12) is fixed on the side wall of the support plate (11), an output shaft (18) is arranged at one end of the servo motor (12), a driving wheel (17) is connected at one end of the output shaft (18), a driven wheel (16) meshed with the driving wheel (17) is arranged at one side of the driving wheel (17), a transmission shaft (13) is connected on the side surface of the driven wheel (16), the transmission shaft (13) is movably connected on a stabilizer bar (15), and the stabilizer bar (15) is fixed on the support plate (11), the end part of the transmission shaft (13) is connected with a first gear (14), and the first gear (14) is meshed with the clamping mechanism (2).

7. The preparation method of the nano composite codeposition enhanced metal-based gradient coating according to claim 6, characterized in that a clamping mechanism (2) for clamping a sample is arranged on the shell (1), the clamping mechanism (2) is matched with a quenching mechanism (3), the quenching mechanism (3) is arranged inside the shell (1), the clamping mechanism (2) is connected with a cooling mechanism (4), and the cooling mechanism (4) is arranged inside the shell (1);

the clamping mechanism (2) comprises a lifting plate (21) arranged inside the support plate (11), a plurality of clamping teeth (26) which are uniformly distributed are arranged on the side wall of the lifting plate (21), an upper clamping plate (22) is fixed at the bottom of the lifting plate (21), and the upper clamping plate (22) is of a U-shaped structure with a downward opening;

fixture (2) are still including fixing branch (25) in shell (1) bottom, the cover is equipped with rather than sliding connection's slide bar (24) on branch (25), the top of slide bar (24) is fixed with lower plate (23), lower plate (23) are the ascending U type structure of opening.

8. The method for preparing the nano composite codeposition enhanced metal-based gradient coating according to claim 7, characterized in that the cooling mechanism (4) comprises an engaging wheel (43) matched with the lifting plate (21), the engaging wheel (43) is engaged with the second gear (41) through a transmission rod (42), the transmission rod (42) is movably connected with a pull rod (44), and the top of the pull rod (44) is fixed on the shell (1);

cooling body (4) still include third gear (45) with second gear (41) looks meshing, third gear (45) side is fixed with bull stick (47), the end connection of bull stick (47) has flabellum (48), bull stick (47) and Y type pole (46) swing joint, the top of Y type pole (46) is fixed on shell (1).

9. The preparation method of the nano composite codeposition reinforced metal-based gradient coating according to claim 8, characterized in that the quenching mechanism (3) comprises a hydraulic cylinder (31) fixed on the shell (1), the hydraulic cylinder (31) is connected with a hydraulic rod (34), the end of the hydraulic rod (34) is connected with a bracket (37), the bracket (37) is of an L-shaped structure, the end of the bracket (37) is fixedly connected with a conductive wheel (35), the middle part of the conductive wheel (35) is provided with a rotating pin (36) penetrating through the conductive wheel and fixedly connected with an electrode (38), and the conductive wheel (35) is rotatably connected with the electrode (38);

quenching mechanism (3) are still including fixing stabilizer plate (33) on shell (1) inner wall, the inside of stabilizer plate (33) is fixed with wire (32), be connected with butt head (310) on wire (32), butt head (310) set up the inside at conductive wheel (35), the cover is equipped with spring (311) on butt head (310), spring (311) set up the inside at conductive wheel (35), the lateral wall of butt head (310) is provided with gag lever post (39), gag lever post (39) and conductive wheel (35) sliding connection, butt head (310) and electrode (38) surface looks butt.

Technical Field

The invention relates to the technical field of electrodeposition, in particular to a preparation method of a nanometer cBN-hBN composite codeposition enhanced metal-based gradient coating.

Background

The composite electrodeposition is that on the basis of the traditional electroplating process, one or more insoluble solid particles are added into electroplating solution to realize the codeposition of the solid particles and metal ions, thereby obtaining a composite plating layer with the dual properties of the solid particles and metal.

Under the influence of the nano reinforcing phase, the nano composite coating mainly has the following characteristics: (1) a multiphase structure; due to the dispersion strengthening effect of the nanoparticles, the parent phase metal grains are refined into the nanocrystals, so that the nanocrystals have a multi-phase structure. (2) Excellent mechanical properties; the nano particles generate a fine-grain strengthening effect on the composite coating in the process of codeposition with metal ions, so that the coating has a more compact structure and finer grains, the microstructure of the composite coating is effectively improved, and the mechanical property of the composite coating is improved. In addition, compared with micron-sized second-phase particles, the nano particles can better improve the hardness and the wear resistance of the composite coating. Therefore, the nano composite coating can further improve the performance of the composite coating.

Before strengthening, the combination between the plating layer and the matrix is mainly through mechanical occlusion, the crystal grains are embedded on the surface of the matrix like 'rivets', and the combination force between the crystal grains is mainly mechanical adhesive force and also has certain physical adhesive force and chemical acting force. However, this physical adhesion force is liable to cause the plating layer to be detached from the surface of the substrate after the sample surface is pressed by pressure or friction, and the plating layer has a low strength to cause poor effect in use of the sample, which affects the plating result.

Disclosure of Invention

The invention aims to solve the problems and provide a preparation method of a nanometer cBN-hBN composite codeposition reinforced metal-based gradient coating.

The invention realizes the aim through the following technical scheme, and the preparation method of the nanometer cBN-hBN composite codeposition enhanced metal-based gradient coating comprises the following steps:

step S1: pretreating the surface of the substrate;

step S2: on the surface of the matrix processed in the step S1, cubic structure and hexagonal structure isomorphism isomers are used as a reinforcing phase, metal is used as a mother phase of an electroplated layer, and the content of the reinforcing phase in the electroplating solution is gradually increased and is changed in a gradient manner during electroplating to form a particle reinforced metal-based gradient composite plated layer;

step S3: putting the plating layer obtained in the step S2 in an electric contact strengthening device for electric contact strengthening, wherein;

the electrode is tightly pressed on the surface of a workpiece under the driving of the cylinder, the pressure between the electrode and the workpiece is controlled to be 98N, the electrode rotates reversely due to friction force, the electrode is enabled to do feed motion on the surface of a sample while rotating, when the electrode does feed motion, large current is introduced, and the current generates resistance heat with large energy density on the surface of the workpiece to quench and strengthen the surface of a coating.

Preferably, the pretreatment in step S1 is to sequentially sand the substrate, remove oil, activate with weak acid, and rinse the substrate surface with deionized water between each step.

Preferably, in the step S2, the reinforcing phase is one of diamond-graphite and cBN-hBN, and the grain size of the reinforcing phase is 10-80 nm.

Preferably, the metal-based plating mother phase in the step S2 is one of Ni, Ni-P, Ni-W, Ni-Co, Ni-Fe, Ni-Mo, Ni-Mn, Ni-Co-Mn and Ni-Fe-P.

Preferably, in the step S3, the pressure between the electrode and the workpiece is 49-196N, the feeding speed of the electrode is 0.5-2 mm/min, and the current is 30-50 kA.

Preferably, the electrical contact strengthening device in step S3 includes a housing, a support plate is fixed to a top of the housing, a through groove adapted to the clamping mechanism is formed in a middle of the support plate, a servo motor is fixed to a side wall of the support plate, an output shaft is arranged at one end of the servo motor, a driving wheel is connected to one end of the output shaft, a driven wheel engaged with the driving wheel is arranged at one side of the driving wheel, a transmission shaft is connected to a side surface of the driven wheel, the transmission shaft is movably connected to a stabilizer bar, the stabilizer bar is fixed to the support plate, a first gear is connected to an end of the transmission shaft, and the first gear is engaged with the clamping mechanism.

Preferably, the shell is provided with a clamping mechanism for clamping the sample, the clamping mechanism is matched with the quenching mechanism, the quenching mechanism is arranged inside the shell, the clamping mechanism is connected with the cooling mechanism, and the cooling mechanism is arranged inside the shell;

preferably, the clamping mechanism comprises a lifting plate arranged inside the support plate, a plurality of clamping teeth are uniformly distributed on the side wall of the lifting plate, an upper clamping plate is fixed at the bottom of the lifting plate, and the upper clamping plate is of a U-shaped structure with a downward opening;

preferably, fixture is still including fixing the branch in the shell bottom, the cover is equipped with rather than sliding connection's slide bar on the branch, the top of slide bar is fixed with the lower plate, the lower plate is the ascending U type structure of opening.

Preferably, the cooling mechanism comprises a meshing wheel matched with the lifting plate, the meshing wheel is meshed with the second gear through a transmission rod, the transmission rod is movably connected with a pull rod, and the top of the pull rod is fixed on the shell;

preferably, the cooling mechanism further comprises a third gear meshed with the second gear, a rotating rod is fixed to the side face of the third gear, fan blades are connected to the end portion of the rotating rod, the rotating rod is movably connected with the Y-shaped rod, and the top of the Y-shaped rod is fixed to the shell.

Preferably, the quenching mechanism comprises a hydraulic cylinder fixed on the shell, the hydraulic cylinder is connected with a hydraulic rod, the end part of the hydraulic rod is connected with a support, the support is of an L-shaped structure, the end part of the support is fixedly connected with a conductive wheel, the middle part of the conductive wheel is provided with a rotating pin penetrating through the conductive wheel and fixedly connected with an electrode, and the conductive wheel is rotatably connected with the electrode;

preferably, the quenching mechanism further comprises a stabilizing plate fixed on the inner wall of the shell, a lead is fixed inside the stabilizing plate, a butting head is connected to the lead and arranged inside the conductive wheel, a spring is sleeved on the butting head and arranged inside the conductive wheel, a limiting rod is arranged on the side wall of the butting head, the limiting rod is connected with the conductive wheel in a sliding mode, and the butting head is abutted to the surface of the electrode.

The invention has the beneficial effects that:

(1) the composite coating is wear-resistant and wear-reducing integrated based on the high hardness of the cubic structure reinforcing phase and the laminar slip property of the hexagonal structure reinforcing phase;

(2) the performance of the metal-based composite coating is greatly improved through the integration effect of the nanometer reinforcing phase and the gradient distribution thereof;

(3) by strengthening the electric contact of the plating layer, the quality of the surface and the interior of the plating layer is improved, the bonding between the plating layer and the substrate is changed from mechanical bonding to metallurgical bonding, and the bonding force between the plating layer and the substrate is greatly improved.

(4) The output shaft is accurately controlled to rotate through the arranged servo motor, when the output shaft rotates, the output shaft drives the driving wheel to rotate, the driving wheel rotates to drive the driven wheel meshed with the driving wheel to rotate, the driven wheel drives the first gear to rotate, and the first gear drives the lifting plate meshed with the first gear to move; the sample can be stably clamped by the arranged clamping mechanism, so that the sample is uniformly heated when moving, and the sample is quenched; the cooling mechanism can complete quenching and blow and cool the moving sample, so that the sample can be quenched conveniently.

(5) The lifting plate is arranged to drive the meshing wheel to rotate, the meshing wheel drives the second gear to rotate, the second gear rotates to drive the third gear below the second gear to rotate, when the third gear rotates, the third gear drives the rotating rod to rotate, the rotating rod rotates to drive the fan blades connected with the rotating rod to rotate, and therefore the fan blades generate wind towards the sample, and then some stabilities on the surface of the sample are taken away, and therefore the sample can be quenched conveniently.

(6) The hydraulic rod is driven forwards through the arranged hydraulic cylinder, the hydraulic rod moves to further drive the support to move, after the support moves, the support drives the conductive wheels to move synchronously, when the conductive wheels move, the electrodes between the conductive wheels can move synchronously along with the conductive wheels until the electrodes are extruded with the sample and tightly pressed on the surface of the workpiece; when the sample upwards moved, the electrode rotated, and at this moment, the electrode both ends contacted with the butt head all the time, formed a closed return circuit with two electrode connection through the wire that sets up for the electrode generates heat fast after the circular telegram.

(7) Because the bonding force between the electroplated layer and the matrix is mainly mechanical adhesive force, the electroplated layer is easy to peel off under the working condition of high contact stress. Therefore, post-treatment of the plating layer is required to improve the bonding force. The electric contact strengthening is a technology that large current is conducted on two contact surfaces to generate resistance heat between the two surfaces, the surface performance of parts is improved under the environment of high temperature and high pressure, and the binding force between a coating and a substrate is improved. In the process of electrical contact strengthening, the surface of the coating is affected by the pressure of the electrode wheel, the high peak is affected by the shearing force and pressed into the low peak, the gap on the surface of the coating is filled, the tissue becomes uniform and compact, the horizontal crack inside the coating is pressed under the action of the pressure, and the high contact pressure between the electrode and the workpiece reduces the hole and the gap inside the coating. Meanwhile, according to the Joule-Lenz law and the heat conduction law, the large current passing between the coating and the electrode generates huge heat to melt and solidify the coating, the cracks in the inner vertical direction are fused, and partial holes disappear. The high temperature and high pressure improve the quality of the surface and the interior of the coating. After the strengthening, under the action of heat, the bonding mode between the plating layer and the substrate is changed, and the bonding force between the plating layer and the substrate is improved. After quenching, the coating has stronger adhesive force with the matrix, and the coating is not easy to separate from the matrix.

Drawings

FIG. 1 is a flow chart of a method for preparing a nano composite codeposition enhanced metal-based gradient coating according to the present invention;

FIG. 2 is a schematic view of the overall structure of the electrical contact enhancing apparatus of the present invention;

FIG. 3 is a schematic diagram of the internal structure of the electrical contact enhancing apparatus of the present invention;

FIG. 4 is a schematic diagram of a transmission structure of a servo motor on the electrical contact strengthening device;

FIG. 5 is an enlarged view of the structure at A of FIG. 2;

FIG. 6 is an enlarged view of the structure at B in FIG. 3;

FIG. 7 is an enlarged view of the structure of FIG. 3 at C;

in the figure: 1. a housing; 11. a support plate; 12. a servo motor; 13. a drive shaft; 14. a first gear; 15. a stabilizer bar; 16. a driven wheel; 17. a driving wheel; 18. an output shaft; 2. a clamping mechanism; 21. a lifting plate; 22. an upper splint; 23. A lower splint; 24. a slide bar; 25. a strut; 26. clamping teeth; 3. a quenching mechanism; 31. a hydraulic cylinder; 32. a wire; 33. A stabilizing plate; 34. a hydraulic lever; 35. a conductive wheel; 36. rotating the pin; 37. a support; 38. an electrode; 39. a limiting rod; 310. A butting head; 311. a spring; 4. a cooling mechanism; 41. a second gear; 42. a transmission rod; 43. an engaging wheel; 44. a pull rod; 45. a third gear; 46. a Y-shaped rod; 47. a rotating rod; 48. a fan blade.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Referring to fig. 1-7, a method for preparing a nanocomposite co-deposited enhanced metal-based gradient coating includes the following steps:

step S1: pretreating the surface of the substrate;

step S2: on the surface of the matrix processed in the step S1, cubic structure and hexagonal structure isomorphism isomers are used as a reinforcing phase, metal is used as a mother phase of an electroplated layer, and the content of the reinforcing phase in the electroplating solution is gradually increased and is changed in a gradient manner during electroplating to form a particle reinforced metal-based gradient composite plated layer;

step S3: putting the plating layer obtained in the step S2 in an electric contact strengthening device for electric contact strengthening, wherein;

the electrode is tightly pressed on the surface of a workpiece under the driving of the cylinder, the pressure between the electrode and the workpiece is controlled to be 98N, the electrode rotates reversely due to friction force, the electrode is enabled to do feed motion on the surface of a sample while rotating, when the electrode does feed motion, large current is introduced, and the current generates resistance heat with large energy density on the surface of the workpiece to quench and strengthen the surface of a coating.

And the pretreatment in the step S1 comprises the steps of sequentially carrying out sand paper grinding, oil removal and weak acid activation on the substrate, and washing the surface of the substrate by deionized water among the steps.

In the step S2, the reinforcing phase is one of diamond-graphite and cBN-hBN, and the particle size of the reinforcing phase is 10-80 nm.

In the step S2, the metal-based plating mother phase is one of Ni, Ni-P, Ni-W, Ni-Co, Ni-Fe, Ni-Mo, Ni-Mn, Ni-Co-Mn and Ni-Fe-P.

In the step S3, the pressure between the electrode and the workpiece is 49-196N during electric contact strengthening, the electrode feeding speed is 0.5-2 mm/min, and the current is 30-50 kA.

Example 1:

preparing the nano diamond-graphite composite codeposition enhanced nickel-based gradient plating layer on the surface of 316L stainless steel by adopting a suspension method.

316L stainless steel with the thickness of 40mm multiplied by 5mm is selected as the electroplating base material, and the base material is pretreated as follows before the experiment: polishing with water sand paper to remove surface defects, polishing with No. 40 metallographic sand paper, ultrasonic treating in acetone for 15min to remove oil, washing with deionized water, soaking in 5% dilute hydrochloric acid (HCl) for 10s to improve the binding force between the coating and the substrate, washing with deionized water, and drying for later use.

Nickel is selected as electroplating matrix metal, artificial diamond particles and graphite particles are selected as reinforcing phases, the average particle size of the diamond particles is 40nm, and the average particle size of the graphite particles is 60 nm. The diamond particles are subjected to hydrophilization treatment before electroplating as follows: ultrasonic cleaning in acetone solution, washing with deionized water, boiling in 10% dilute nitric acid (HNO3) solution for 30min, washing with deionized water, boiling in 10% dilute sodium hydroxide (NaOH) solution for 30min, washing with deionized water, and oven drying. The graphite particles are pretreated as follows: sequentially treating with dilute 10% dilute nitric acid (HNO3) and 5% dilute hydrochloric acid (HCl) to remove impurities, discarding some insoluble substances at the bottom, repeatedly washing with deionized water to neutrality, and drying.

The composite electroplating solution required by the suspension method consists of diamond particles, graphite particles and nickel plating solution, and the main components and parameters are shown in table 1.

TABLE 1 major Components and parameters of the composite electroplating solution

The anode is a pure nickel plate, pretreated 316L stainless steel is used as a cathode, the areas of the cathode plate and the anode plate are equal, and the distance between the electrodes is 30 mm. After the two polar plates are horizontally placed in the prepared composite electroplating suspension, the magnetic rotor keeps a proper speed, so that the diamond particles and the graphite particles are kept in a suspension state in the electroplating solution, the content of the diamond particles and the graphite particles in the electroplating solution is gradually increased in a gradient change during electroplating, the content of the diamond particles is increased from 0 to 40g/L, the content of the graphite particles is increased from 0 to 30g/L, and the nano-diamond-graphite composite nickel-based gradient coating is prepared. Electrodeposition was carried out using a galvanostatic method. And (3) taking out the sample after the electroplating is finished, washing the sample with clear water, then putting the sample into an ultrasonic cleaner for ultrasonic cleaning for 10min (removing diamond and graphite particles which do not enter the coating), washing with water and drying. Table 2 shows the plating process conditions.

TABLE 2 gradient coating process conditions for nano-diamond-graphite composite nickel-based coating

Test conditions	Parameter(s)
		Temperature (. degree.C.)	40
Current density (A/dm2)	2
		Time (h)	1
Speed of agitation (rpm)	600

The electrode is tightly pressed on the surface of a workpiece under the driving of the cylinder, the pressure between the electrode and the workpiece is controlled to be 98N, the electrode rotates in the reverse direction due to friction force, the electrode is enabled to do feed motion on the surface of a sample while rotating, and the feed speed is 1 mm/min. When the electrode does feed motion, a large current of 40kA is applied, and resistance heat with high energy density is generated on the surface of the workpiece by the current to quench and strengthen the surface of the coating.

Example 2:

an electrodeposition method is used for preparing the nanometer cBN-hBN composite codeposition enhanced Ni-P gradient coating on the surface of the TC4 titanium alloy matrix.

The TC4 titanium alloy with the thickness of 40mm multiplied by 5mm is selected as the electroplating base material, and the base material is pretreated as follows before the experiment: polishing by using abrasive paper to remove an oxidation film, wherein the process mainly comprises the step of roughly removing the oxidation film on the surface of the titanium alloy substrate; chemical degreasing, which is mainly used for removing residual grease and dirt on the surface of a sample; and (3) acid pickling and activating, namely, acid pickling and activating the TC4 titanium alloy substrate to completely remove an oxide film and corrosion products on the surface of the substrate. And (4) washing the surface of the sample by using deionized water among the steps, and finally drying for later use.

Ni-P was selected as a plating matrix, cubic boron nitride (cBN) particles and hexagonal boron nitride (hBN) particles were selected as a reinforcing phase, the cBN particles had an average particle size of 30nm and the hBN particles had an average particle size of 50 nm. The pre-treatment of the cBN and hBN particles was as follows: washing with clear water, soaking in 1:1 nitric acid for 3 hr, soaking in 1:1 hydrochloric acid for 1 hr, washing with acid, and separating.

The composite plating solution consisted of cBN particles, hBN particles and Ni-P plating solution, the main components and parameters are shown in Table 3.

TABLE 3 main Components and parameters of the composite electroplating solution

The anode material is ruthenium titanium alloy, the pretreated TC4 titanium alloy is used as a cathode, the areas of cathode and anode plates are equal, and the distance between the anode and the cathode plates is 30 mm. After the two polar plates are horizontally placed in the prepared composite electroplating suspension liquid, the magnetic rotor keeps a proper speed, so that the cBN particles and the hBN particles keep a suspension state in the electroplating liquid, the content of the cBN particles and the content of the hBN particles in the electroplating liquid are gradually increased to form gradient change during electroplating, the content of the cBN particles is increased from 0 to 50g/L, the content of the hBN particles is increased from 0 to 40g/L, and the nanometer cBN-hBN composite Ni-P-based gradient coating is prepared. Electrodeposition was carried out using a galvanostatic method. And (3) taking out the sample after the electroplating is finished, washing the sample with clear water, then putting the sample into an ultrasonic cleaner for ultrasonic cleaning for 10min (removing cBN and hBN particles which do not enter the coating), washing with water and drying. Table 4 shows the plating process conditions.

TABLE 4 nanometer cBN-hBN composite Ni-P based gradient coating process conditions

Test conditions	Parameter(s)
		Temperature (. degree.C.)	60
Current density (A/dm2)	3
		Time (h)	1
Speed of agitation (rpm)	700

The electrode is tightly pressed on the surface of a workpiece under the driving of the cylinder, the pressure between the electrode and the workpiece is controlled to be 98N, the electrode rotates in the reverse direction due to friction force, the electrode is enabled to do feed motion on the surface of a sample while rotating, and the feed speed is 1.2 mm/min. When the electrode does feed motion, a large current of 45kA is applied, and the current is used as the resistance heat with large energy density on the surface of the workpiece to quench and strengthen the surface of the coating. Comparative example 1:

compared with the example 1, only the diamond particles are added, the graphite particles are not added, and other process parameters are the same, namely the wear-resistant nano-diamond composite codeposition enhanced nickel-based gradient coating is prepared on the surface of 316L stainless steel by a suspension method.

Comparative example 2:

compared with the example 1, only graphite particles are added, diamond particles are not added, and other process parameters are the same, namely the antifriction (self-lubricating) nano graphite composite codeposition enhanced nickel-based gradient coating is prepared on the surface of 316L stainless steel by a suspension method.

Comparative example 3:

compared with the example 1, the diamond particles and the graphite particles are not added, and the rest technological parameters are the same, namely, the nickel coating is prepared on the surface of 316L stainless steel by adopting a suspension method.

Comparative example 4:

compared with the example 2, only cBN particles are added, no hBN particles are added, and other process parameters are the same, namely the wear-resistant nano cBN composite codeposition is adopted on the surface of the TC4 titanium alloy to enhance the Ni-P based gradient coating.

Comparative example 5:

compared with the example 2, only the hBN particles are added, the cBN particles are not added, and other process parameters are the same, namely, the Ni-P-based gradient coating is enhanced on the surface of the TC4 titanium alloy by preparing the antifriction (self-lubricating) nano hBN composite codeposition.

Comparative example 6:

compared with the example 2, the Ni-P plating layer is prepared on the surface of the TC4 titanium alloy by adding neither cBN particles nor hBN particles and the rest technological parameters are the same.

A pin disc friction wear testing machine is adopted, a lower sample is a prepared coating, an upper sample is a GCr15 bearing steel ball with the diameter of phi 8mm, normal load is applied through weights, frictional resistance formed by point contact between the upper sample and the lower sample can cause micro change of an elastic cantilever beam, the change can be acquired and converted into electric signals by sensors on two sides, and a corresponding friction coefficient is obtained through subsequent processing.

The parameters of the friction test are as follows: load 0.49N, rotation radius 9mm, rotation speed 100rpm, sampling interval 100ms, time 20 min. Since the early stage of the test is in an unstable stage, running and mixing are required to be carried out, the composite coating runs at 100rpm for 10min, and the average value of the friction data of the last 10min is taken as the final friction coefficient of the sample.

And taking the depth of a grinding mark after the coating is worn as an evaluation index of the wear resistance of the composite coating. The wear resistance test is carried out on a self-made pin disc friction wear testing machine, and a GCr15 bearing steel ball with the diameter of 8mm is selected as an upper sample. The wear test was performed under dry friction conditions. The experimental parameters were: load 10N, rotation radius 11mm, rotation speed 100rpm, time 30 min.

For example 1, comparative example 2, comparative example 3; the friction coefficient and the wear resistance were measured for example 2, comparative example 4, comparative example 5, and comparative example 6, respectively, and the results are shown in tables 5 and 6. As can be seen from tables 5 and 6, the graphite or hBN particles are independently added in the nickel or Ni-P coating, and the friction coefficient can be greatly reduced and the wear resistance is greatly improved by depending on the self-lubricating property of the graphite or hBN; diamond or cBN particles are independently added into the nickel or Ni-P coating, and the wear resistance can be greatly improved and the friction coefficient is reduced to a certain degree by depending on the high hardness of the diamond or cBN; the composite plating layer is wear-resistant and wear-reducing integrated by adding diamond-graphite or cBN-hBN particles into the nickel or Ni-P plating layer and depending on the self-lubricating property of the layered graphite or hBN with the high-hardness hexagonal structure of the cubic diamond or cBN, the composite plating layer has the best wear resistance although the friction is slightly higher than that of the composite plating layer added with the graphite or hBN alone. The friction coefficient of the composite coating layer added with the diamond or cBN particles is lower than that of the original nickel or Ni-P coating layer, and the phenomenon is caused because the stronger the cutting capability of the diamond or cBN particles on the bearing steel ball of the upper sample is, the more the cut abrasive dust is, the abrasive dust is accumulated on the surface of the upper sample, the micro rolling effect is realized between the composite coating layer and the friction pair of the bearing steel ball, and the friction coefficient of the coating layer is reduced.

TABLE 5 nanodiamond-graphite composite nickel-based gradient coating and comparative example test results thereof

Test specimen	Average coefficient of friction	Depth of grinding crack/mum
			Example 1	0.37	11.4
Comparative example 1	0.71	15.9
			Comparative example 2	0.23	25.6
Comparative example 3	0.86	47.3

TABLE 6 nanometer cBN-hBN composite Ni-P based gradient coating and comparative example test results thereof

Test specimen	Average coefficient of friction	Depth of grinding crack/mum
			Example 2	0.41	14.8
Comparative example 4	0.68	17.3
			Comparative example 5	0.26	29.1
Comparative example 6	0.83	43.5

Specifically, the electrical contact strengthening device in step S3 includes a housing 1, a supporting plate 11 is fixed to a top of the housing 1, a through groove adapted to the clamping mechanism 2 is formed in a middle of the supporting plate 11, a servo motor 12 is fixed to a side wall of the supporting plate 11, an output shaft 18 is arranged at one end of the servo motor 12, a driving wheel 17 is connected to one end of the output shaft 18, a driven wheel 16 engaged with the driving wheel 17 is arranged at one side of the driving wheel 17, a transmission shaft 13 is connected to a side surface of the driven wheel 16, the transmission shaft 13 is movably connected to a stabilizer bar 15, the stabilizer bar 15 is fixed to the supporting plate 11, a first gear 14 is connected to an end of the transmission shaft 13, and the first gear 14 is engaged with the clamping mechanism 2; the servo motor 12 is arranged to accurately control the rotation of the output shaft 18, when the output shaft 18 rotates, the output shaft 18 drives the driving wheel 17 to rotate, the driving wheel 17 rotates to drive the driven wheel 16 meshed with the driving wheel to rotate, the driven wheel 16 drives the first gear 14 to rotate, and the first gear 14 drives the lifting plate 21 meshed with the first gear to move; the sample can be stably clamped by the arranged clamping mechanism 2, so that the sample is uniformly heated when moving, and the sample is quenched; the quenching is completed through the arranged cooling mechanism 4, and the moving sample can be blown to reduce the temperature, so that the sample can be quenched conveniently.

Specifically, be provided with fixture 2 that is used for the centre gripping sample on the shell 1, fixture 2 cooperatees with quenching mechanism 3, quenching mechanism 3 sets up the inside at shell 1, fixture 2 is connected with cooling body 4, cooling body 4 sets up the inside at shell 1.

Specifically, the clamping mechanism 2 comprises a lifting plate 21 arranged inside the support plate 11, a plurality of clamping teeth 26 which are uniformly distributed are arranged on the side wall of the lifting plate 21, an upper clamping plate 22 is fixed at the bottom of the lifting plate 21, and the upper clamping plate 22 is of a U-shaped structure with a downward opening. Thereby can stretch out and draw back through the upper clamp plate 22 that sets up and carry out the joint to the sample and fix, the inside of upper clamp plate 22 is provided with the extension spring.

Specifically, fixture 2 is still including fixing the branch 25 in shell 1 bottom, the cover is equipped with rather than sliding connection's slide bar 24 on the branch 25, slide bar 24's top is fixed with lower plate 23, lower plate 23 is the ascending U type structure of opening. The side wall of the sample can be clamped through the arranged lower clamping plate 23, and when the sample moves upwards, the lower clamping plate 23 drives the sliding rod 24 to move upwards synchronously.

Specifically, the cooling mechanism 4 includes an engaging wheel 43 adapted to the lifting plate 21, the engaging wheel 43 is engaged with the second gear 41 through a transmission rod 42, the transmission rod 42 is movably connected with a pull rod 44, and the top of the pull rod 44 is fixed on the housing 1. The lifting plate 21 is arranged to drive the meshing wheel 43 to rotate, the meshing wheel 43 drives the second gear 41 to rotate, the second gear 41 rotates to drive the third gear 45 which is arranged below the second gear to rotate and is meshed with the second gear, when the third gear 45 rotates, the third gear 45 drives the rotating rod 47 to rotate, the rotating rod 47 rotates to drive the fan blades 48 which are connected with the rotating rod to rotate, and therefore the fan blades 48 generate wind towards the sample, and then some stability on the surface of the sample is taken away, and therefore the sample can be conveniently quenched.

Specifically, the cooling mechanism 4 further includes a third gear 45 engaged with the second gear 41, a rotating rod 47 is fixed on a side surface of the third gear 45, a fan blade 48 is connected to an end of the rotating rod 47, the rotating rod 47 is movably connected with a Y-shaped rod 46, and a top of the Y-shaped rod 46 is fixed on the housing 1.

Specifically, the quenching mechanism 3 comprises a hydraulic cylinder 31 fixed on the housing 1, the hydraulic cylinder 31 is connected with a hydraulic rod 34, the end of the hydraulic rod 34 is connected with a bracket 37, the bracket 37 is of an L-shaped structure, the end of the bracket 37 is fixedly connected with a conductive wheel 35, the middle of the conductive wheel 35 is provided with a rotating pin 36 penetrating through the conductive wheel and fixedly connected with an electrode 38, and the conductive wheel 35 is rotatably connected with the electrode 38. The hydraulic rod 34 is driven forwards through the arranged hydraulic cylinder 31, the hydraulic rod 34 moves to further drive the bracket 37 to move, after the bracket 37 moves, the bracket 37 drives the conductive wheels 35 to move synchronously, when the conductive wheels 35 move, the electrodes 38 between the conductive wheels 35 can move synchronously along with the conductive wheels 35 until the electrodes 38 are extruded with the sample and are tightly pressed on the surface of the workpiece; when the sample moves upwards, the electrode 38 rotates, at this time, both ends of the electrode 38 are always in contact with the abutting head 310, and the two electrodes 38 are connected through the arranged conducting wire 32 to form a closed loop, so that the electrode 38 heats rapidly after being electrified.

Specifically, the quenching mechanism 3 further comprises a stabilizing plate 33 fixed on the inner wall of the housing 1, a wire 32 is fixed inside the stabilizing plate 33, the wire 32 is connected with a butting head 310, the butting head 310 is arranged inside the conductive wheel 35, a spring 311 is sleeved on the butting head 310, the spring 311 is arranged inside the conductive wheel 35, a limit rod 39 is arranged on the side wall of the butting head 310, the limit rod 39 is connected with the conductive wheel 35 in a sliding manner, and the butting head 310 is abutted to the surface of the electrode 38.

The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and the embodiments and descriptions described above are only illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the present invention, which fall within the scope of the claims of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.