阅读说明：本技术 一种NbC/Fe2B复合梯度耐磨涂层及其制备方法 (NbC/Fe2B composite gradient wear-resistant coating and preparation method thereof ) 是由 魏祥 刘晓威 杨泽壬 陈志国 郝鹏磊 于 2020-08-10 设计创作，主要内容包括：本发明公开了一种NbC/Fe<Sub>2</Sub>B复合梯度耐磨涂层及其制备方法,属于耐磨涂层领域。本发明中所述涂层包含NbC和Fe<Sub>2</Sub>B两种硬质相,其中NbC耐磨涂层位于复合涂层的外侧,Fe<Sub>2</Sub>B耐磨涂层位于NbC耐磨涂层与基体材料之间。其制备过程包括选用以渗碳体为强化相的钢铁材料(0.3%≤C wt%≤1.2%)为基体材料,并对其进行表面处理,以纯Nb棒为电极材料,采用电火花沉积工艺首先制备NbC强化的纳米晶涂层,再对该涂层进行固体渗硼处理。本发明中制备的涂层在工件截面上形成了微观组织和力学性能的梯度结构,能显著提高涂层的综合性能,电火花沉积的纳米晶涂层中包含大量的晶界和位错,能极大的降低渗硼温度,缩短渗硼时间。(The invention discloses NbC/Fe 2 A B composite gradient wear-resistant coating and a preparation method thereof belong to the field of wear-resistant coatings. The coating of the present invention comprises NbC and Fe 2 B two hard phases, wherein NbC wear-resistant coating is positioned at the outer side of the composite coating, and Fe 2 The B wear-resistant coating is positioned between the NbC wear-resistant coating and the base material. The preparation process comprises selecting steel material (0.3-1.2 wt%) with cementite as strengthening phase as matrix material, performing surface treatment, preparing NbC strengthened nanocrystalline coating by using pure Nb rod as electrode material and performing solid boronizing treatment on the coating. The coating prepared by the method forms a microstructure and a gradient structure with mechanical property on the cross section of a workpiece, can obviously improve the comprehensive property of the coating, and the nano-crystalline coating deposited by electric spark contains a large amount of crystal boundaries and dislocation, so that the boronizing temperature can be greatly reduced, and the boronizing time can be shortened。)

1. NbC/Fe₂The B composite gradient wear-resistant coating is characterized in that: the composite gradient wear-resistant coating comprises NbC and Fe₂B two hard phases, NbC wear-resistant coating outside the composite coating, Fe₂B wear-resistant coatingPositioned between the NbC wear-resistant coating and the substrate material, the thickness of the NbC wear-resistant coating is more than or equal to 2 mu m and less than or equal to 50 mu m, and Fe₂The thickness of the wear-resistant coating B is more than or equal to 5 mu m and less than or equal to 100 mu m, and the matrix material is a steel material taking cementite as a strengthening phase.

2. NbC/Fe according to claim 1₂The B composite gradient wear-resistant coating is characterized in that: the mass fraction of carbon element in the steel material taking cementite as the strengthening phase is more than or equal to 0.3 percent and less than or equal to 1.2 percent by weight of C.

3. NbC/Fe according to claim 1₂The preparation method of the B composite gradient wear-resistant coating is characterized in that the coating is prepared by adopting an electric spark deposition process, and the specific process steps are as follows:

(1) for NbC/Fe₂B, carrying out surface treatment on the base material prepared by the composite gradient wear-resistant coating, wherein the surface treatment comprises derusting and deoiling, and if the surface has cracks, carrying out turning to eliminate the crack layer;

(2) adopting a pure Nb rod as an electrode material, preparing an NbC reinforced nanocrystalline coating on the surface of the matrix material treated in the step (1) by adopting electric spark deposition, and adopting inert gas for protection in the deposition process, wherein the specific process parameters of the deposition are as follows: the output power is 1500-3000W, the output voltage is 120-300V, and the deposition rate is 0.5-10min/cm²；

(3) Carrying out boronizing treatment on the workpiece obtained in the step (2) by adopting a solid boronizing process, wherein the boronizing process parameters are as follows: the boronizing temperature is 850-1100 ℃, and the boronizing heat preservation time is 10-600 min.

4. NbC/Fe according to claim 3₂The preparation method of the B composite gradient wear-resistant coating is characterized by comprising the following steps: the NbC-strengthened nanocrystalline coating comprises two phases of a solid solution of NbC and Nb in Fe, and the grain sizes of the two phases are both nano-scale.

5. The method of claim 3NbC/Fe₂The preparation method of the B composite gradient wear-resistant coating is characterized by comprising the following steps: in the NbC strengthened nanocrystalline coating, the NbC phase is generated in situ, and the carbon element for generating the NbC phase comes from a matrix material.

6. NbC/Fe according to claim 3₂The preparation method of the B composite gradient wear-resistant coating is characterized by comprising the following steps: the NbC phase in the NbC wear-resistant coating comes from the NbC phase in the NbC reinforced nanocrystalline coating, and the NbC phase generated by the reaction of Nb in solid solution of Nb in Fe in the NbC reinforced nanocrystalline coating and carbon element in the boronizing process.

7. NbC/Fe according to claim 3₂The preparation method of the B composite gradient wear-resistant coating is characterized by comprising the following steps: the boronizing agent is LSB-II type boronizing agent.

Technical Field

The invention relates to a wear-resistant coating and a preparation method thereof, in particular to NbC/Fe₂B composite gradient wear-resistant coating and a preparation method thereof.

Background

The surface engineering technology can prepare a coating or a cladding with special performances of wear resistance, corrosion resistance and the like on the surface of the material, which are different from those of a base material, and can change the form, chemical components and tissue structure of the surface and the near-surface area of the material by the most economical and effective method, thereby realizing the strengthening, modification, repair and remanufacture of the surface of the material. The technology is widely applied in practice and creates great economic benefits.

The spark deposition process is a surface treatment technique which utilizes spark discharge to melt and transfer electrode materials to the surface of a base material so as to form a coating with specific properties. The deposition principle is that when the electrode material as the anode is infinitely close to the base material (workpiece) as the cathode in a rotating or vibrating mode, short-period and high-current electric pulse discharge is utilized to generate high temperature of 5000-10000 ℃ to instantly melt or even gasify a tiny area infinitely close to the electrode material and the base material, and under the action of electric field force, the melted electrode material is transferred to the surface of the base material to be melted and rapidly solidified with the melted electrode material, so that a deposition layer in metallurgical combination is formed. Compared with other surface technologies, the electric spark deposition process has the following advantages: (1) the energy input is low, the matrix is kept at room temperature, and the heat affected zone is small, so that the influence of the matrix can be ignored; (2) the coating and the matrix are in metallurgical bonding, and the bonding strength is high and is obviously superior to that of thermal spraying; (4) the equipment is cheap and the operation is simple; (5) the method is suitable for in-situ or online repair, and is very important for repairing large workpieces or online equipment; (6) the molten electrode material can be rapidly solidified on the surface of the base material, and can form a nanocrystalline or even amorphous coating, so that the performance of the material is further improved. However, in the actual production of the wear-resistant coating prepared by the electric spark deposition, in order to obtain excellent wear-resistant performance, the electrode material used by the coating is generally high-hardness cemented carbide or cermet. Although such coatings have better wear resistance and are used in many applications, they also have some disadvantages. Height ofThe high hardness of hard alloy or metal ceramic comes from a large amount of brittle hard phase, and the electric spark deposition is a surface treatment technology for rapid solidification, so that longitudinal cracks are easily generated in the prepared coating in the electric spark deposition process, the improvement of the wear resistance of the coating is not facilitated, and the coating is easy to peel due to the existence of large thermal stress, so that the practical coating thickness is about 50 mu m generally, and the wear-resistant coating with large thickness cannot be obtained. In order to obtain a larger coating thickness and avoid the generation of cracks in the coating, recently, Koelreuteria paniculata et al reported the work of preparing Nb coating on the surface of hot-work die steel H13 by using Nb bars with better plasticity as electrode materials based on electric spark deposition, and the results show that the coating has continuous and compact cross-section structure, no obvious defects and contains Fe₂Nb and Fe_0.2Nb_0.8The hardness of the two phases, namely the coating reaches 642HV and is 3.2 times that of the matrix, under the same friction and wear test condition, the wear quality is only 1/3 of the matrix material, and the service life of the H13 steel die is remarkably prolonged (Koelreuteria, et al. H13 steel surface electric spark deposition Nb coating organization and performance research, surface technology, 2019,48 (1): 285-289.). NbC has a ratio of Fe₂Nb and Fe_0.2Nb_0.8The two phases have much higher hardness and have been widely used in the fields of high temperature alloys (patent No.: CN 108467959B), cermets (patent No.: CN 105779951A), thin film materials (patent No.: CN 103894757A) and coatings (patent No.: CN103526198A, CN 103255414A). On the other hand, studies show that the composite gradient coating can further remarkably improve the comprehensive performance of the coating compared with a single coating, but the NbC/Fe is related to the current situation₂The research of the B composite gradient wear-resistant coating is not reported in a public way.

Disclosure of Invention

The invention aims to provide high-performance NbC/Fe₂B composite gradient wear-resistant coating and a preparation method thereof.

In order to achieve the above purpose, the invention adopts the following technical scheme:

the composite gradient wear-resistant coating comprises NbC and Fe₂B two hard phases, wherein NbC wear-resistant coating is positioned at the outer side of the composite coating, and Fe₂The B wear-resistant coating is positioned between the NbC wear-resistant coating and the base material, wherein the thickness of the NbC wear-resistant coating is more than or equal to 2 mu m and less than or equal to 50 mu m, and Fe₂The thickness of the B wear-resistant coating is more than or equal to 5 μm and less than or equal to 100 μm.

The preparation method is carried out by adopting an electric spark deposition process, and the specific process steps are as follows:

(1) for NbC/Fe₂B, carrying out surface treatment on a steel material (the mass fraction of carbon is more than or equal to 0.3% and less than or equal to C wt% and less than or equal to 1.2%) prepared by the composite gradient wear-resistant coating by using a cementite strengthening phase, wherein the surface treatment comprises derusting and deoiling, and if cracks exist on the surface, carrying out row cutting to eliminate a crack layer;

(2) adopting a pure Nb rod as an electrode material to carry out electric spark deposition to prepare the NbC reinforced nanocrystalline coating, adopting inert gas to carry out protection in the deposition process, wherein the specific process parameters of the deposition are as follows: the output power is 1500-3000W, the output voltage is 120-300V, and the deposition rate is 0.5-10min/cm²。

(3) Carrying out boronizing treatment on the workpiece obtained in the step (2) by adopting a solid boronizing process, wherein the boronizing process parameters are as follows: the boronizing temperature is 850-1100 ℃, and the boronizing heat preservation time is 10-600 min.

The boronizing agent is LSB-II type boronizing agent.

Due to the adoption of the technical scheme, the NbC/Fe alloy provided by the invention₂The B composite gradient wear-resistant coating and the preparation method thereof have the beneficial effects that the prepared composite gradient coating consists of an NbC wear-resistant coating at the outer layer and Fe at the inner layer₂B, the wear-resistant coating forms a microstructure and a gradient structure of mechanical properties on the cross section, which is beneficial to improving the comprehensive properties of the coating; because of the extremely fast cooling rate in the electric spark deposition process, the grain size in the prepared NbC reinforced nanocrystalline coating reaches the nanometer level, the number of surface defects (grain boundaries) in the coating is greatly increased, and a large amount of line defects (dislocations) are formed because the solid solution of Nb with good plasticity in Fe deforms under the action of thermal stress, and the existence of the two defects can be used asThe diffusion energy barrier of boron atoms is greatly reduced by the diffusion channel of boron atoms in the boronizing process, so that the boronizing temperature is greatly reduced, the boronizing heat preservation time is shortened, and the improvement of the performance of a workpiece and the energy conservation are realized; and because of the extremely fast cooling rate in the electric spark deposition process, the crystal grain for preparing the NbC strengthened nanocrystalline coating is in a nanometer level, the plasticity and toughness of the coating are improved through fine grain strengthening, and the coating can release a large amount of thermal stress through plastic deformation in the fast solidification process through the combined action of the crystal grain and the solid solution phase of Nb in Fe with good plasticity in the nanocrystalline coating, thereby effectively avoiding the generation of longitudinal cracks in the NbC strengthened nanocrystalline coating and being beneficial to the increase of the thickness of the NbC strengthened nanocrystalline coating; the strengthening phase in the matrix material is cementite (Fe)₃C) The stability of the material is lower than that of NbC, so that a prerequisite is created for generating NbC in the process of electric spark deposition; in the preparation of NbC-containing coatings reported in the literature, carbon elements in NbC are externally added, such as in the form of graphite, and the carbon elements are difficult to be uniformly distributed in the coatings under the process condition; the high-hardness NbC phase in the NbC reinforced nanocrystalline coating is generated in situ, so that the interface bonding strength of the NbC phase and the Nb solid solution phase in Fe is high, and the improvement of the comprehensive performance of the NbC reinforced nanocrystalline coating is facilitated.

Drawings

FIG. 1 shows NbC/Fe in the present invention₂B typical microstructure picture of composite gradient wear-resistant coating.

FIG. 2 shows NbC/Fe in the present invention₂And B, typical X-ray diffraction pattern of the composite gradient wear-resistant coating.

Detailed Description

The present invention will be further described with reference to the following examples.