阅读说明：本技术 耐熔融AlSi腐蚀的稀土氧化物改性MoB-CoCr梯度涂层及其制备方法 (Rare earth oxide modified MoB-CoCr gradient coating resistant to molten AlSi corrosion and preparation method thereof ) 是由 刘侠 张世宏 沈成龙 薛召露 王硕煜 倪振航 于 2020-12-22 设计创作，主要内容包括：本发明公开一种耐熔融AlSi腐蚀的稀土氧化物改性MoB-CoCr梯度涂层及其制备方法,通过首先在试样表面喷涂CoCrWC粘接层,然后喷涂掺杂Y-2O-3的MoB-CoCr为工作层的方法制备出的稀土氧化物改性MoB-CoCr梯度涂层,内层为包覆在辊件表面的CoCrWC涂层,外层为封孔后的稀土氧化物改性MoB-CoCr涂层；这种耐熔融AlSi腐蚀的稀土氧化物改性MoB-CoCr梯度涂层,具有优异的耐熔融铝硅腐蚀性能,可提高钢厂对沉没辊的利用率,提高产品生产的效率和质量。(The invention discloses a rare earth oxide modified MoB-CoCr gradient coating resistant to molten AlSi corrosion and a preparation method thereof 2 O 3 The MoB-CoCr is a rare earth oxide modified MoB-CoCr gradient coating prepared by the method with the working layer, the inner layer is a CoCrWC coating coated on the surface of a roller, and the outer layer is a hole-sealed rare earth oxide modified MoB-CoCr coating; the rare earth oxide modified MoB-CoCr gradient coating resistant to molten AlSi corrosion has excellent molten aluminum silicon corrosion resistance, can improve the utilization rate of a sink roller in a steel mill, and improves the production efficiency and quality of products.)

1. The rare earth oxide modified MoB-CoCr gradient coating resistant to molten AlSi corrosion is characterized in that the inner layer is a CoCrWC coating coated on the surface of a roller, and the outer layer is a hole-sealed rare earth oxide modified MoB-CoCr coating.

2. The molten AlSi corrosion resistant rare earth oxide modified MoB-CoCr gradient coating as claimed in claim 1, wherein the CoCrWC coating comprises, by mass, 25-32% of Cr, 4-5% of W, 1-2% of C, and the balance of Co, and the MoB-CoCr coating comprises, by mass, 13-14% of B, 32-33% of Mo, 23-25% of Cr, and the balance of Co.

3. The method of preparing a molten AlSi corrosion resistant rare earth oxide modified MoB-CoCr gradient coating according to claim 1 or 2, comprising the steps of:

s1: cleaning and sandblasting the surface of the stainless steel substrate;

s2: preparing a CoCrWC bonding layer on the surface of a substrate by using a supersonic flame spraying method, wherein the thickness of the coating is 100-110 mu m;

s3: preparation of rare earth oxide modified MoB-CoCr coating by using supersonic flame spraying method and doping with Y₂O₃The mass fraction of the powder is 1-10%, the rest is MoB-CoCr powder, and the thickness of the coating is 150-;

s4: to doping Y₂O₃MoB-CoCr gradient coatingAnd (3) hole sealing treatment, namely performing ultrasonic cleaning on the prepared coating, uniformly coating a hole sealing agent on the surface of the dried coating by using a brush, and then placing a sample with the surface uniformly coated with the hole sealing agent in a box-type resistance furnace to promote the hole sealing agent to permeate into the coating and be cured.

4. The method for preparing the molten AlSi corrosion resistant rare earth oxide modified MoB-CoCr gradient coating according to claim 3, wherein the step S1 further comprises preheating the sample before spraying, wherein the preheating temperature is 80-100 ℃.

5. The method for preparing the molten AlSi corrosion resistant rare earth oxide modified MoB-CoCr gradient coating according to claim 3, wherein the spraying process parameters of the CoCrWC bonding layer in the step S2 are as follows: oxygen flow is 50-55 m³The flow rate of kerosene is 25-27L/h, the spraying distance is 320mm, the length of a gun tube is 4 inches, the powder feeding rate is 75-85 g/min, and the scanning speed of a spray gun is 700-900 mm/s.

6. The method for preparing a rare earth oxide modified MoB-CoCr gradient coating resistant to corrosion by molten AlSi according to claim 3, wherein the spraying process parameters of the rare earth oxide modified MoB-CoCr coating in the step S3 are as follows: oxygen flow is 50-55 m³The flow rate of kerosene is 29-31L/h, the spraying distance is 320mm, the length of a gun barrel is 6 inches, the powder feeding rate is 75-85 g/min, and the scanning speed of a spray gun is 700-900 mm/s.

7. The method of claim 3, wherein Y in step S3 is Y in the step of preparing a gradient coating of molten AlSi corrosion resistant rare earth oxide modified MoB-CoCr₂O₃The powder was mixed with the MoB-CoCr powder by mechanical stirring.

8. The method for preparing the molten AlSi corrosion resistant rare earth oxide modified MoB-CoCr gradient coating according to claim 3, wherein the sealant in the step S4 mainly comprises Cr₂O₃、SiO₂、Al₂O₃And BN.

9. The method for preparing the molten AlSi corrosion resistant rare earth oxide modified MoB-CoCr gradient coating according to claim 3, wherein in the step S4, the temperature of the box type resistance furnace is set to be 550 ℃, and the holding time is 4-5 h.

Technical Field

The invention relates to the technical field of metal ceramic composite coatings, in particular to a rare earth oxide modified MoB-CoCr gradient coating resistant to molten AlSi corrosion and a preparation method thereof.

Background

In the hot dip aluminum-silicon wire, the temperature range of the aluminum-silicon liquid is generally 670-. In addition, the aluminum-silicon liquid has very small infiltration diameter and strong infiltration capacity. Therefore, the molten aluminum-silicon liquid with higher temperature and stronger corrosiveness puts more severe requirements on the corrosion resistance of the coating material.

The ternary boride is a interstitial phase compound, comprises an M-M metal bond, a B-B covalent bond and a B-M ionic bond, has the advantages of high melting point, high hardness, high wear resistance, high corrosion resistance and the like, and has poor wettability with an aluminum alloy melt, so the ternary boride is often used for manufacturing a molten metal corrosion resistant protective coating.

MoB-CoCr is a new type metal ceramic coating, and its phase is ternary boride CoMo₂B₂And a small amount of binary boride MoB, has excellent corrosion resistance in molten metal and alloy and higher wear resistance, and is applied to the fields of hot galvanizing and hot dip aluminum zinc. Meanwhile, the coating has high application potential in the field of hot-dip aluminum silicon. However, as the etching time increases, defects such as pores and cracks exist in the HVOF spraying MoB-CoCr coating, the matching performance of the thermal physical property between the coating and the substrate is poor, the thermal expansion coefficient of the coating is lower than that of the substrate, and stress concentration and cracks are generated at the interface of the defects and the coating in a high-temperature environment. The final coating failed under the synergistic effect of corrosion and stress.

In view of the above-mentioned drawbacks, the inventors of the present invention have finally obtained the present invention through a long period of research and practice.

Disclosure of Invention

The invention aims to solve the problem of corrosion resistance of molten aluminum-silicon liquid with higher temperature and stronger corrosivity to a coating material, and provides a rare earth oxide modified MoB-CoCr gradient coating resistant to molten AlSi corrosion and a preparation method thereof.

In order to achieve the purpose, the invention discloses a rare earth oxide modified MoB-CoCr gradient coating resistant to corrosion of molten AlSi, wherein the inner layer is a CoCrWC coating coated on the surface of a roller, and the outer layer is a rare earth oxide modified MoB-CoCr coating subjected to hole sealing. The CoCrWC coating consists of Cr: 25-32%, W: 4-5%, C: 1-2% and the balance of Co, wherein the MoB-CoCr coating comprises the following components in percentage by mass: 13-14%, Mo: 32-33%, Cr: 23-25% and the balance of Co.

The invention also discloses a preparation method of the molten AlSi corrosion resistant rare earth oxide modified MoB-CoCr gradient coating, which comprises the following steps:

s1: cleaning and sandblasting the surface of the stainless steel substrate;

s2: preparing a CoCrWC bonding layer on the surface of a substrate by using a supersonic flame spraying method, wherein the thickness of the coating is 100-110 mu m;

s3: preparation of rare earth oxide modified MoB-CoCr coating by using supersonic flame spraying method and doping with Y₂O₃The mass fraction of the powder is 1-10%, the rest is MoB-CoCr powder, and the thickness of the coating is 150-;

s4: to doping Y₂O₃The MoB-CoCr gradient coating hole sealing treatment comprises the steps of carrying out ultrasonic cleaning on a prepared coating, then uniformly coating a hole sealing agent on the surface of the dried coating by using a brush, and then placing a sample with the surface uniformly coated with the hole sealing agent in a box-type resistance furnace to promote the hole sealing agent to permeate into the coating and be cured.

And the step S1 further comprises preheating the sample before spraying, wherein the preheating temperature is 80-100 ℃.

The spraying process parameters of the CoCrWC bonding layer in the step S2 are as follows: oxygen flow is 50-55 m³The flow rate of kerosene is 25-27L/h, the spraying distance is 320mm, the length of a gun tube is 4 inches, the powder feeding rate is 75-85 g/min, and the scanning speed of a spray gun is 700-900 mm/s.

The spraying process parameters of the rare earth oxide modified MoB-CoCr coating in the step S3 are as follows: oxygen flow is 50-55 m³The flow rate of kerosene is 29-31L/h, the spraying distance is 320mm, the length of a gun barrel is 6 inches, the powder feeding rate is 75-85 g/min, and the scanning speed of a spray gun is 700-900 mm/s.

The above-mentionedY in step S3₂O₃The powder was mixed with the MoB-CoCr powder by mechanical stirring.

The sealant in the step S4 mainly comprises Cr₂O₃、SiO₂、Al₂O₃And BN.

In the step S4, the set temperature of the box type resistance furnace is 550 ℃, and the heat preservation time is 4-5 h.

Compared with the prior art, the invention has the beneficial effects that: the rare earth oxide modified MoB-CoCr gradient coating prepared by the method has the advantages of few surface defects, low porosity, high density and low aluminum-silicon liquid permeability, the CoCrWC bonding layer is added, the accumulation and discontinuity of thermal stress in the coating are reduced, the bonding force between the coating layers is strong, and the coating layers are not easy to crack. The method can obtain a high-quality coating which has good mechanical property, thermal shock resistance, excellent molten aluminum silicon liquid corrosion resistance and is suitable for the harsh service environment of a sink roller/a stabilizing roller.

Drawings

FIG. 1 is a SEM topography of a cross section of a coating prepared in example 3 of the invention;

FIG. 2 is an XRD pattern of a coating prepared in example 3 of the present invention;

FIG. 3 is SEM cross-sectional shapes of different areas of the coating prepared in example 1 after 3 days of corrosion by molten AlSi;

FIG. 4 is SEM (cross-sectional view) shapes of different areas of the coating prepared in example 2 of the invention after being corroded by molten AlSi for different time;

FIG. 5 is SEM cross-sectional shapes of different areas of the coating prepared in example 3 of the present invention after being corroded for 9 days by molten AlSi.

FIG. 6 is an XRD pattern of a coating after molten AlSi etching of the coating prepared in example 2 of the present invention.

FIG. 7 is an XRD pattern of a coating after molten AlSi etching of a coating prepared in example 3 of the present invention.

FIG. 8 is a graph comparing the crack density of coatings prepared in examples 2 and 3 of the present invention after molten AlSi etching for various periods of time.

Detailed Description

The above and further features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.

Example 1

The preparation method of the MoB-CoCr coating comprises the following steps:

step 1, degreasing and decontaminating the surface of a sample on the surface of 316L stainless steel until the surface is smooth, then performing sand blasting treatment by adopting 24-mesh brown corundum, wherein the sand blasting pressure is 0.5MPa, the surface of the sample after sand blasting reaches Sa 3-grade roughness, and finally cleaning by using alcohol and drying.

And 2, preheating the sample before spraying, wherein the preheating temperature is 80-100 ℃.

And step 3: preparing a MoB-CoCr coating on the surface of a substrate by using a supersonic flame spraying method, wherein the MoB-CoCr coating consists of the following components in percentage by mass: 12.7%, Mo: 32%, Cr: 27.8%, Co: 27.5% composition. The spraying process comprises the following steps: oxygen flow 53m³The flow rate of kerosene is 30L/h, the spraying distance is 320mm, the length of a gun barrel is 6 inches, the powder feeding rate is 80g/min, the scanning speed of a spray gun is 800mm/s, and the thickness of a coating is 100 mu m.

And 4, step 4: and (3) sealing holes of the MoB-CoCr gradient coating, carrying out ultrasonic cleaning on the prepared coating, and then uniformly coating a sealing agent on the surface of the dried coating by using a brush. Then, the sample with the surface uniformly coated with the hole sealing agent is placed in a box-type resistance furnace to promote the hole sealing agent to permeate into the coating and be cured, wherein the main component of the hole sealing agent is Cr₂O₃、SiO₂、Al₂O₃And BN. The set temperature of the box type resistance furnace is 550 ℃, and the heat preservation time is 4-5 h.

And carrying out a molten aluminum silicon corrosion experiment on the prepared MoB-CoCr coating. The experimental composition is Al: 88%, Si: 12 percent (mass fraction) of aluminum-silicon alloy is used as a corrosion medium. And (3) placing a proper amount of aluminum-silicon alloy in a crucible at room temperature, setting a temperature rise program, and slowly soaking the sample in aluminum-silicon liquid along with the fixture after the temperature of the furnace chamber reaches a set value and the aluminum-silicon alloy is completely melted. After soaking, the materials were taken out, and the experimental results are shown in FIG. 3.

Example 2

The preparation method of the MoB-CoCr gradient coating resistant to molten AlSi corrosion comprises the following steps:

step 1, degreasing and decontaminating the surface of a sample on the surface of 316L stainless steel until the surface is smooth, then performing sand blasting treatment by adopting 24-mesh brown corundum, wherein the sand blasting pressure is 0.5MPa, the surface of the sample after sand blasting reaches Sa 3-grade roughness, and finally cleaning by using alcohol and drying.

Step 2: preheating the sample before spraying, wherein the preheating temperature is 80-100 ℃.

And step 3: preparing a CoCrWC inner coating on the surface of a matrix by using a supersonic flame spraying method, wherein Co-based alloy powder consists of Cr: 28%, W: 5%, Co: 66%, C:1 percent of the components. The particle size of the powder is 15-60 μm. The spraying process comprises the following steps: oxygen flow 53m³The flow rate of kerosene is 26L/h, the spraying distance is 320mm, the length of a gun barrel is 4 inches, the powder feeding rate is 80g/min, the scanning speed of a spray gun is 800mm/s, and the thickness of a bonding layer is 100 mu m.

And 4, step 4: preparing a MoB-CoCr coating by using a supersonic flame spraying method, wherein the MoB-CoCr coating consists of the following components in percentage by mass: 12.7%, Mo: 32%, Cr: 27.8%, Co: 27.5% composition. The coating thickness was 150. mu.m. The spraying process comprises the following steps: oxygen flow rate 55m³The flow rate of kerosene is 30L/h, the spraying distance is 320mm, the length of a gun barrel is 6 inches, the powder feeding rate is 80g/min, and the scanning speed of a spray gun is 800 mm/s.

And 5: and (3) sealing holes of the MoB-CoCr gradient coating, carrying out ultrasonic cleaning on the prepared coating, and then uniformly coating a sealing agent on the surface of the dried coating by using a brush. Then, the sample with the surface uniformly coated with the hole sealing agent is placed in a box-type resistance furnace to promote the hole sealing agent to permeate into the coating and be cured, wherein the main component of the hole sealing agent is Cr₂O₃、SiO₂、Al₂O₃And BN. The set temperature of the box type resistance furnace is 550 ℃, and the heat preservation time is 4-5 h.

And carrying out a molten aluminum silicon corrosion experiment on the prepared MoB-CoCr gradient coating resistant to molten AlSi corrosion. The experimental composition is Al: 88%, Si: 12 percent (mass fraction) of aluminum-silicon alloy is used as a corrosion medium. And (3) placing a proper amount of aluminum-silicon alloy in a crucible at room temperature, setting a temperature rise program, and slowly soaking the sample in aluminum-silicon liquid along with the fixture after the temperature of the furnace chamber reaches a set value and the aluminum-silicon alloy is completely melted. After soaking, the materials were taken out, and the experimental results are shown in FIG. 4.

Example 3

The preparation method of the molten AlSi corrosion resistant rare earth oxide modified MoB-CoCr gradient coating comprises the following steps:

step 1, degreasing and decontaminating the surface of a sample on the surface of 316L stainless steel until the surface is smooth, then performing sand blasting treatment by adopting 24-mesh brown corundum, wherein the sand blasting pressure is 0.5MPa, the surface of the sample after sand blasting reaches Sa 3-grade roughness, and finally cleaning by using alcohol and drying.

Step 2: preheating the sample before spraying, wherein the preheating temperature is 80-100 ℃.

And step 3: preparing a CoCrWC bonding coating on the surface of a matrix by using a supersonic flame spraying method, wherein Co-based alloy powder consists of Cr: 28%, W: 5%, Co: 66%, C:1 percent of the components. The spraying process comprises the following steps: oxygen flow 53m³The flow rate of kerosene is 26L/h, the spraying distance is 320mm, the length of a gun barrel is 4 inches, the powder feeding rate is 80g/min, the scanning speed of a spray gun is 800mm/s, and the thickness of a bonding layer is 100 mu m.

And 4, step 4: preparation of Y Using a supersonic flame spray Process₂O₃Coating of/MoB-CoCr with Y₂O₃Mixing the powder and MoB-CoCr powder according to a mass ratio, wherein the MoB-CoCr coating consists of the following components in percentage by mass: 12.7%, Mo: 32%, Cr: 27.8%, Co: 27.5% composition. Using mechanical mixing means to mix Y₂O₃The powder is uniformly mixed in MoB-CoCr powder, wherein Y₂O₃The mass fraction of the powder is 0.5-3%. The coating thickness was 150. mu.m. The spraying process comprises the following steps: the oxygen flow is 55m3/h, the kerosene flow is 30L/h, the spraying distance is 320mm, the length of a gun tube is 6 inches, the powder feeding rate is 80g/min, and the scanning speed of a spray gun is 800 mm/s.

And 5: the hole sealing treatment of the MoB-CoCr gradient coating is characterized in that the prepared coating is subjected to ultrasonic cleaning, and then a hole sealing agent is uniformly coated on the surface of the dried coating by using a brush. Then, the sample with the surface uniformly coated with the hole sealing agent is placed in a box-type resistance furnace to promote the hole sealing agent to permeate into the coating and be cured, wherein the main component of the hole sealing agent is Cr₂O₃、SiO₂、Al₂O₃And BN. The set temperature of the box type resistance furnace is 550 DEG CAnd keeping the temperature for 4-5 hours.

And carrying out a molten aluminum silicon corrosion experiment on the prepared oxide modified MoB-CoCr gradient coating resistant to molten AlSi corrosion. The experimental composition is Al: 88%, Si: 12 percent (mass fraction) of aluminum-silicon alloy is used as a corrosion medium. And (3) placing a proper amount of aluminum-silicon alloy in a crucible at room temperature, setting a temperature rise program, and slowly soaking the sample in aluminum-silicon liquid along with the fixture after the temperature of the furnace chamber reaches a set value and the aluminum-silicon alloy is completely melted. After soaking, the sample was taken out, and the experimental results are shown in FIG. 5.

FIG. 1 is a SEM topography of a cross section of a coating prepared in example 3 of the invention; in the figure, Y is arranged from top to bottom in sequence₂O₃The coating comprises a/MoB-CoCr coating working layer, a CoMoW bonding layer and a stainless steel matrix, and has uniform and compact structure, tight combination and porosity<1% bonding strength>70 MPa. FIG. 2 is an XRD pattern of a coating prepared according to a third embodiment of the present invention, the coating consisting essentially of CoMo₂B₂CoMoB, and small amounts of MoB.

3-5, longitudinal cracks and transverse cracks penetrating through the coating appear in the MoB-CoCr coating without the adhesive layer in example 1 in three days; in the embodiment 2, transverse cracks and longitudinal cracks are not generated after the CoCrW bonding layer is added for nine days, which shows that the thermal stress of the working layer and the matrix can be effectively reduced by adding the bonding layer; example 3 addition of Y to MoB-CoCr layer₂O₃After 9 days of corrosion, the coating had a good cross-section and showed virtually no cracks. Thus, doping with Y₂O₃The bonding strength of the phase interface in the coating is improved, the toughness of the coating is improved, the crack propagation is effectively avoided, and the service life of the coating is further prolonged.

As can be seen in FIGS. 6 to 7, the gradient coating prepared in example 2 has corrosion products Mo (Si, Al)2 and a small amount of CoAl after 3 days of corrosion, and the coating prepared in example 3 has corrosion products Mo (Si, Al)2 and a small amount of CoAl after Y₂O₃After the content is 1-2%, the coating is not corroded after 9 days, and no corrosion product appears, which shows that the coating has good corrosion resistance after being doped with rare earth oxide.

Fig. 8 gives a quantitative analysis of cracks after corrosion of the coating. Comparative undopedThe coating can be seen, and it can be seen that doping Y₂O₃And then, the density of cracks in the coating is obviously reduced, the crack initiation and propagation rate is greatly reduced, and the molten aluminum silicon corrosion resistance of the coating is obviously improved.

The foregoing is merely a preferred embodiment of the invention, which is intended to be illustrative and not limiting. It will be understood by those skilled in the art that various changes, modifications and equivalents may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.