CN115354371A - Method for improving mechanical property of multi-element Ni-based alloy coating by element doping and heat treatment - Google Patents

Abstract

The invention discloses a method for improving the mechanical property of a multi-element Ni-based alloy coating by element doping and heat treatment, which comprises the steps of pretreating a metal substrate by mechanical pretreatment, degreasing, activation and the like, heating the metal substrate in an electroplating solution in a water bath and simultaneously carrying out direct current deposition, adding a small amount of sulfate solution in the electrodeposition process to prepare a deposition multi-element Ni-Mo-W alloy coating, and carrying out vacuum heat treatment on the coating obtained by deposition to obtain the multi-element Ni-Mo-W alloy coating. The method has the advantages of simple operation, easy control of conditions and good repeatability, not only can effectively improve the corrosion resistance of the plating layer, but also more importantly solves the problem of insufficient wear resistance of the Ni-based plating layer after annealing treatment, and provides a guiding function for researching the improvement of the wear resistance and high temperature resistance of other metal plating layers.

Description

A method of element doping and heat treatment to improve the mechanical properties of multi-component Ni-based alloy coatings method

technical field

The invention belongs to the field of alloy coating preparation, and in particular relates to a method for improving the mechanical properties of multi-element Ni-based alloy coating by element doping and heat treatment.

Background technique

Electroplated Ni-based alloy coating has good physical, chemical and mechanical properties, and is widely used in petrochemical industry, aerospace industry, machinery manufacturing industry, electronic communication industry, etc. Among them, the Ni-W coating has good corrosion resistance and wear resistance, as well as good thermal stability and density, but there are also some problems in the electroplating Ni-W layer, such as the coating is easy to peel off, and the toughness is relatively weak in the deposited state. Low, poor ductility, not impact resistant, high overall corrosion resistance but prone to pitting corrosion, etc. Compared with the Ni-W coating, the presence of Mo element in the Ni-Mo-W coating can significantly reduce the internal stress of the coating, so that the coating has more excellent comprehensive mechanical properties. The macroscopic physical properties of the material are often determined by its microstructure, and the change of the process determines the microstructure of the coating. Adding one or more alloying elements to the Ni-Mo-W coating can further optimize the Ni-W-based solid solution or amorphous The corrosion resistance and wear resistance of the alloy, and with the increase of the alloy element content, the solid solution strengthening effect of the Ni-Mo-W alloy increases significantly, and at an appropriate annealing temperature, due to the emergence of the grain boundary relaxation phenomenon, the grain boundary The defects are reduced, which can make the Ni-Mo-W-based coating have higher hardness, wear resistance and corrosion resistance.

Contents of the invention

The purpose of the present invention is to solve the deficiencies of the prior art, to provide a method for element doping and heat treatment to improve the mechanical properties of multi-element Ni-based alloy coatings, the process is simple to operate, the conditions are easy to control, and the repeatability is good. The prepared coating and substrate Good bonding, good film quality, good hardness and wear resistance, suitable for surface treatment of various hardware products, pipe fittings, zippers, plaques, springs and other metal materials.

To achieve the above object, the present invention adopts the following technical solutions:

A method for element doping and heat treatment to improve the mechanical properties of a multi-element Ni-based alloy coating, which is to reduce the grain size of the coating by doping W and Mo elements, and reduce the internal stress of the coating through a certain heat treatment process, so that the obtained alloy coating has excellent The comprehensive mechanical properties; its specific operation is as follows:

1) Mechanically pretreat the metal substrate to make the surface smooth, then degrease the surface with a degreasing agent and perform ultrasonic cleaning, and then activate the surface of the brass sheet to remove the oxide layer;

2) Conduct DC electrodeposition while heating the treated metal substrate in a water bath in the electroplating solution to obtain a deposited multi-component Ni-Mo-W alloy coating; during the electrodeposition process, add a certain amount of sulfate solution to the electroplating solution , and use a magnetic stirrer with ultrasonic emission function to ultrasonically vibrate at a frequency of 40~60kHz, and stir at a rate of 5~15 r/min to make it uniform;

3) The deposited coating is subjected to vacuum heat treatment to obtain a multi-component Ni-Mo-W alloy coating.

Further, the metal substrate in step 1) is a brass sheet; the ultrasonic cleaning time is 5-25 minutes.

Further, the activation treatment in step 1) is soaked in dilute hydrochloric acid or dilute sulfuric acid with a volume fraction of 5-15%, until the surface oxide skin is completely dissolved and the inner metal is exposed.

Further, the electroplating solution in step 2) contains nickel sulfate 20~120 g/L, sodium tungstate 5~30 g/L, sodium molybdate 5~20 g/L, ammonium chloride 2~10 g/L, carbonic acid Sodium 5~60g/L, sodium citrate 30~150g/L, sodium lauryl sulfate 0.02~0.25g/L, and its pH is 5~9.

Further, the temperature of the water bath heating in step 2) is 40-70° C., and the time is 5-35 min.

Further, the current density of direct current electrodeposition in step 2) is 1-4 A/dm ³ , and the deposition time is 2-30 min.

Further, the amount of sulfate solution added in step 2) is converted according to its final concentration in the electroplating solution being 0-20 g/L; the sulfate is ferrous sulfate, manganese sulfate, cobalt sulfate, copper sulfate one or more of.

Further, the vacuum heat treatment in step 3) is to keep the temperature at 300-500°C for 30-300 min, then cool down to room temperature with the furnace, and then break the vacuum and take it out.

In the present invention, the process conditions have an important influence on the electrodeposition. The concentration of the main salt in the electroplating multi-component Ni-Mo-W alloy coating has a significant impact on the alloy content in the coating, and the content of alloy elements in the coating will increase with the increase of the concentration of sodium tungstate and sulfate. The increase in the content of alloying elements in the coating will reduce the grain size of the coating and play a role in refining the grains. By analyzing the XRD diffraction pattern of the coating, it can be seen that when the content of alloy elements is low, the multi-component Ni-Mo-W alloy coating is a replacement solid solution with alloy elements as the solute and Ni as the solvent. At the same time, as the content of alloying elements in the coating increases, the friction coefficient of the coating decreases and the wear resistance becomes better, because the replacement of alloying element atoms plays a solid solution strengthening role in the Ni lattice. In addition, the addition of W element can effectively reduce the internal stress of the coating. With the increase of W content in the coating, the hardness of the coating increases slowly, and the content of W element is controlled at about 4 at%. In addition, heat treatment will make the grain coarse and reduce the hardness of the coating. Vacuum heat treatment at 400 °C can effectively reduce the grain size and internal stress, and improve the comprehensive mechanical properties of the coating.

Significant advantage of the present invention is:

The process of the invention has simple operation, easy control of conditions, good repeatability, good combination of deposited coating and substrate, good film forming quality, and good wear resistance, corrosion resistance and thermal stability.

The present invention effectively reduces the crystal grain size of the coating through the addition of Mo and W elements, and reduces the internal stress of the coating through a certain heat treatment process, so that the coating has more excellent comprehensive mechanical properties. The multi-component Ni-Mo-W alloy coating prepared by electrodeposition in this method may become a strong candidate for metal protective coatings in high friction and wear environments.

Description of drawings

Figure 1 is the XRD patterns of Ni-Mo-W coatings with different W element contents prepared in Examples 1, 2 and 3. It can be seen from the figure that with the increase of W element content, the grain size of the coating decreases.

Fig. 2 is the XRD pattern of the Ni-Mo-W coating prepared under different heat treatment temperatures of Examples 6, 7 and 8. It can be seen from the figure that with the increase of heat treatment temperature, the degree of crystallization of the coating increases and the grain size increases.

Fig. 3 is a graph showing the hardness of Ni-Mo-W coatings prepared in Examples 1, 2, 3, 4 and Comparative Example 1 as a function of W element content.

Fig. 4 is a graph showing the hardness of the Ni-Mo-W coatings prepared in Examples 3, 9, and 10 changing with the content of Mo element.

Fig. 5 is a graph showing the hardness and modulus of elasticity of Ni-Mo-W coatings prepared in Examples 6, 3, 7 and 8 as a function of heat treatment temperature.

Figure 6 is the microscopic morphology of Ni-Mo-W coatings prepared under different heat treatment temperatures in Examples 6, 3, 7, and 8, where (a) 25°C, (b) 300°C, (c) 400°C, ( d) 500°C.

Detailed ways

The present invention will be further explained below in conjunction with specific examples, but it is not intended to limit the protection scope of the present invention. Those that do not indicate specific techniques and reaction conditions in the examples can be carried out according to techniques or conditions described in documents in this field or product instructions. All reagents, instruments or equipment not indicated by the manufacturer can be obtained commercially.

Example 1

The brass sheet was sanded to make its surface smooth, and then the surface was degreased with a commercial degreasing agent and ultrasonically cleaned for 10 min, and then the surface of the brass sheet was activated with dilute sulfuric acid with a volume fraction of 10% to remove the oxide layer ; Then adopt DC electrodeposition power supply in electroplating solution (containing nickel sulfate 60 g/L, sodium tungstate 10 g/L, sodium molybdate 10 g/L, ammonium chloride 2.6 g/L, sodium carbonate 20 g/L in the electroplating solution g/L, sodium citrate 50 g/L, and sodium lauryl sulfate 0.1 g/L) for 5 min, and the current density was 3 A/dm ³ , and the activated brass sheet was placed in In the energized electroplating solution, heat in a water bath at 50 °C for 20 min. During the deposition process, ferrous sulfate solution was added to the electroplating solution (to make the final concentration of ferrous sulfate in the electroplating solution 5 g/L, and the pH of the electroplating solution was kept at 8.5), and the Under the action of ultrasonic vibration at a frequency of 50 kHz and stirring at a rate of 10 r/min, a deposited multi-component Ni-Mo-W alloy coating was obtained. After the obtained coating was dried to remove moisture, it was kept in a vacuum heat treatment furnace at 400°C for 2 hours, and then cooled to room temperature with the furnace, and then removed by breaking the vacuum to obtain a multi-component Ni-Mo-W alloy coating on the surface of the brass substrate.

Example 2

The brass sheet was sanded to make its surface smooth, and then the surface was degreased with a commercial degreasing agent and ultrasonically cleaned for 10 min, and then the surface of the brass sheet was activated with dilute sulfuric acid with a volume fraction of 10% to remove the oxide layer Then adopt DC electrodeposition power supply in electroplating solution (containing nickel sulfate 60 g/L, sodium tungstate 15 g/L, sodium molybdate 10 g/L, ammonium chloride 2.6 g/L, sodium carbonate 20 g/L in the electroplating solution g/L, sodium citrate 50 g/L, and sodium lauryl sulfate 0.1 g/L) for 5 min, and the current density was 3 A/dm ³ , and the activated brass sheet was placed in In the energized electroplating solution, heat in a water bath at 50 °C for 20 min. During the deposition process, ferrous sulfate solution was added to the electroplating solution (to make the final concentration of ferrous sulfate in the electroplating solution 5 g/L, and the pH of the electroplating solution was kept at 8.5), and the Under the action of ultrasonic vibration at a frequency of 50 kHz and stirring at a rate of 10 r/min, a deposited multi-component Ni-Mo-W alloy coating was obtained. After the obtained coating was dried to remove moisture, it was kept in a vacuum heat treatment furnace at 400°C for 2 hours, and then cooled to room temperature with the furnace, and then removed by breaking the vacuum to obtain a multi-component Ni-Mo-W alloy coating on the surface of the brass substrate.

Example 3

The brass sheet was sanded to make its surface smooth, and then the surface was degreased with a commercial degreasing agent and ultrasonically cleaned for 10 min, and then the surface of the brass sheet was activated with dilute sulfuric acid with a volume fraction of 10% to remove the oxide layer Then adopt DC electrodeposition power supply in electroplating solution (containing nickel sulfate 60 g/L, sodium tungstate 20 g/L, sodium molybdate 10 g/L, ammonium chloride 2.6 g/L, sodium carbonate 20 g/L in the electroplating solution g/L, sodium citrate 50 g/L, and sodium lauryl sulfate 0.1 g/L) for 5 min, and the current density was 3 A/dm ³ , and the activated brass sheet was placed in In the energized electroplating solution, heat in a water bath at 50 °C for 20 min. During the deposition process, ferrous sulfate solution was added to the electroplating solution (to make the final concentration of ferrous sulfate in the electroplating solution 5 g/L, and the pH of the electroplating solution was kept at 8.5), and the Under the action of ultrasonic vibration at a frequency of 50 kHz and stirring at a rate of 10 r/min, a deposited multi-component Ni-Mo-W alloy coating was obtained. After the obtained coating was dried to remove moisture, it was kept in a vacuum heat treatment furnace at 400°C for 2 hours, and then cooled to room temperature with the furnace, and then removed by breaking the vacuum to obtain a multi-component Ni-Mo-W alloy coating on the surface of the brass substrate.

Example 4

The brass sheet was sanded to make its surface smooth, and then the surface was degreased with a commercial degreasing agent and ultrasonically cleaned for 10 min, and then the surface of the brass sheet was activated with dilute sulfuric acid with a volume fraction of 10% to remove the oxide layer Then adopt DC electrodeposition power supply in electroplating solution (containing nickel sulfate 60 g/L, sodium tungstate 25 g/L, sodium molybdate 10 g/L, ammonium chloride 2.6 g/L, sodium carbonate 20 g/L in the electroplating solution g/L, sodium citrate 50 g/L, and sodium lauryl sulfate 0.1 g/L) for 5 min, and the current density was 3 A/dm ³ , and the activated brass sheet was placed in In the energized electroplating solution, heat in a water bath at 50 °C for 20 min. During the deposition process, ferrous sulfate solution was added to the electroplating solution (to make the final concentration of ferrous sulfate in the electroplating solution 5 g/L, and the pH of the electroplating solution was kept at 8.5), and the Under the action of ultrasonic vibration at a frequency of 50 kHz and stirring at a rate of 10 r/min, a deposited multi-component Ni-Mo-W alloy coating was obtained. After the obtained coating was dried to remove moisture, it was kept in a vacuum heat treatment furnace at 400°C for 2 hours, and then cooled to room temperature with the furnace, and then removed by breaking the vacuum to obtain a multi-component Ni-Mo-W alloy coating on the surface of the brass substrate.

Example 5

The brass sheet was sanded to make its surface smooth, and then the surface was degreased with a commercial degreasing agent and ultrasonically cleaned for 10 min, and then the surface of the brass sheet was activated with dilute sulfuric acid with a volume fraction of 10% to remove the oxide layer Then adopt DC electrodeposition power supply in electroplating solution (containing nickel sulfate 60 g/L, sodium tungstate 25 g/L, sodium molybdate 10 g/L, ammonium chloride 2.6 g/L, sodium carbonate 20 g/L in the electroplating solution g/L, sodium citrate 50 g/L, and sodium lauryl sulfate 0.1 g/L) for 5 min, and the current density was 3 A/dm ³ , and the activated brass sheet was placed in In the energized electroplating solution, heat in a water bath at 50 °C for 20 min. During the deposition process, ferrous sulfate solution was added to the electroplating solution (to make the final concentration of ferrous sulfate in the electroplating solution 5 g/L, and the pH of the electroplating solution was kept at 8.5), and the Under the action of ultrasonic vibration at a frequency of 50 kHz and stirring at a rate of 10 r/min, a deposited multi-component Ni-Mo-W alloy coating was obtained. After the obtained coating was dried to remove moisture, it was kept in a vacuum heat treatment furnace at 500°C for 2 hours, and then cooled to room temperature with the furnace, and then the vacuum was broken to take it out, and a multi-component Ni-Mo-W alloy coating was obtained on the surface of the brass substrate.

Example 6

The brass sheet was sanded to make its surface smooth, and then the surface was degreased with a commercial degreasing agent and ultrasonically cleaned for 10 min, and then the surface of the brass sheet was activated with dilute sulfuric acid with a volume fraction of 10% to remove the oxide layer Then adopt DC electrodeposition power supply in electroplating solution (containing nickel sulfate 60 g/L, sodium tungstate 20 g/L, sodium molybdate 10 g/L, ammonium chloride 2.6 g/L, sodium carbonate 20 g/L in the electroplating solution g/L, sodium citrate 50 g/L, and sodium lauryl sulfate 0.1 g/L) for 5 min, and the current density was 3 A/dm ³ , and the activated brass sheet was placed in In the energized electroplating solution, heat in a water bath at 50 °C for 20 min. During the deposition process, ferrous sulfate solution was added to the electroplating solution (to make the final concentration of ferrous sulfate in the electroplating solution 5 g/L, and the pH of the electroplating solution was kept at 8.5), and the Under the action of ultrasonic vibration at a frequency of 50 kHz and stirring at a rate of 10 r/min, a deposited multi-component Ni-Mo-W alloy coating was obtained. After the obtained coating was dried to remove moisture, it was kept in a vacuum heat treatment furnace at 25°C for 2 hours, and then cooled to room temperature with the furnace, and then the vacuum was broken to take it out to obtain a multi-component Ni-Mo-W alloy coating on the surface of the brass substrate.

Example 7

The brass sheet was sanded to make its surface smooth, and then the surface was degreased with a commercial degreasing agent and ultrasonically cleaned for 10 min, and then the surface of the brass sheet was activated with dilute sulfuric acid with a volume fraction of 10% to remove the oxide layer Then adopt DC electrodeposition power supply in electroplating solution (containing nickel sulfate 60 g/L, sodium tungstate 20 g/L, sodium molybdate 10 g/L, ammonium chloride 2.6 g/L, sodium carbonate 20 g/L in the electroplating solution g/L, sodium citrate 50 g/L, and sodium lauryl sulfate 0.1 g/L) for 5 min, and the current density was 3 A/dm ³ , and the activated brass sheet was placed in In the energized electroplating solution, heat in a water bath at 50 °C for 20 min. During the deposition process, ferrous sulfate solution was added to the electroplating solution (to make the final concentration of ferrous sulfate in the electroplating solution 5 g/L, and the pH of the electroplating solution was kept at 8.5), and the Under the action of ultrasonic vibration at a frequency of 50 kHz and stirring at a rate of 10 r/min, a deposited multi-component Ni-Mo-W alloy coating was obtained. After the obtained coating was dried to remove moisture, it was kept in a vacuum heat treatment furnace at 300°C for 2 hours, then cooled to room temperature with the furnace, and then the vacuum was broken to take it out to obtain a multi-component Ni-Mo-W alloy coating on the surface of the brass substrate.

Example 8

The brass sheet was sanded to make its surface smooth, and then the surface was degreased with a commercial degreasing agent and ultrasonically cleaned for 10 min, and then the surface of the brass sheet was activated with dilute sulfuric acid with a volume fraction of 10% to remove the oxide layer Then adopt DC electrodeposition power supply in electroplating solution (containing nickel sulfate 60 g/L, sodium tungstate 20 g/L, sodium molybdate 10 g/L, ammonium chloride 2.6 g/L, sodium carbonate 20 g/L in the electroplating solution g/L, sodium citrate 50 g/L, and sodium lauryl sulfate 0.1 g/L) for 5 min, and the current density was 3 A/dm ³ , and the activated brass sheet was placed in In the energized electroplating solution, heat in a water bath at 50 °C for 20 min. During the deposition process, ferrous sulfate solution was added to the electroplating solution (to make the final concentration of ferrous sulfate in the electroplating solution 5 g/L, and the pH of the electroplating solution was kept at 8.5), and the Under the action of ultrasonic vibration at a frequency of 50 kHz and stirring at a rate of 10 r/min, a deposited multi-component Ni-Mo-W alloy coating was obtained. After the obtained coating was dried to remove moisture, it was kept in a vacuum heat treatment furnace at 500°C for 2 hours, and then cooled to room temperature with the furnace, and then the vacuum was broken to take it out, and a multi-component Ni-Mo-W alloy coating was obtained on the surface of the brass substrate.

Example 9

The brass sheet was sanded to make its surface smooth, and then the surface was degreased with a commercial degreasing agent and ultrasonically cleaned for 10 min, and then the surface of the brass sheet was activated with dilute sulfuric acid with a volume fraction of 10% to remove the oxide layer Then adopt DC electrodeposition power supply in electroplating solution (containing nickel sulfate 60 g/L, sodium tungstate 20 g/L, sodium molybdate 5 g/L, ammonium chloride 2.6 g/L, sodium carbonate 20 g/L in the electroplating solution g/L, sodium citrate 50 g/L, and sodium lauryl sulfate 0.1 g/L) for 5 min, and the current density was 3 A/dm ³ , and the activated brass sheet was placed in In the energized electroplating solution, heat in a water bath at 50 °C for 20 min. During the deposition process, ferrous sulfate solution was added to the electroplating solution (to make the final concentration of ferrous sulfate in the electroplating solution 5 g/L, and the pH of the electroplating solution was kept at 8.5), and the Under the action of ultrasonic vibration at a frequency of 50 kHz and stirring at a rate of 10 r/min, a deposited multi-component Ni-Mo-W alloy coating was obtained. After the obtained coating was dried to remove moisture, it was kept in a vacuum heat treatment furnace at 400°C for 2 hours, and then cooled to room temperature with the furnace, and then removed by breaking the vacuum to obtain a multi-component Ni-Mo-W alloy coating on the surface of the brass substrate.

Example 10

The brass sheet was sanded to make its surface smooth, and then the surface was degreased with a commercial degreasing agent and ultrasonically cleaned for 10 min, and then the surface of the brass sheet was activated with dilute sulfuric acid with a volume fraction of 10% to remove the oxide layer Then adopt DC electrodeposition power supply in electroplating solution (containing nickel sulfate 60 g/L, sodium tungstate 20 g/L, sodium molybdate 15 g/L, ammonium chloride 2.6 g/L, sodium carbonate 20 g/L in the electroplating solution g/L, sodium citrate 50 g/L, and sodium lauryl sulfate 0.1 g/L) for 5 min, and the current density was 3 A/dm ³ , and the activated brass sheet was placed in In the energized electroplating solution, heat in a water bath at 50 °C for 20 min. During the deposition process, ferrous sulfate solution was added to the electroplating solution (to make the final concentration of ferrous sulfate in the electroplating solution 5 g/L, and the pH of the electroplating solution after mixing was maintained at 8.5), and the magnetic Under the action of a stirrer, ultrasonic vibration is performed at a frequency of 50 kHz, combined with stirring at a rate of 10 r/min, to obtain a multi-component Ni-Mo-W alloy coating in a deposited state. After the obtained coating was dried to remove moisture, it was kept in a vacuum heat treatment furnace at 400°C for 2 hours, and then cooled to room temperature with the furnace, and then removed by breaking the vacuum to obtain a multi-component Ni-Mo-W alloy coating on the surface of the brass substrate.

Comparative example 1

The brass sheet was sanded to make its surface smooth, and then the surface was degreased with a commercial degreasing agent and ultrasonically cleaned for 10 min, and then the surface of the brass sheet was activated with dilute sulfuric acid with a volume fraction of 10% to remove the oxide layer ; Then adopt DC electrodeposition power supply in electroplating solution (containing nickel sulfate 60 g/L, sodium tungstate 10 g/L, sodium molybdate 10 g/L, ammonium chloride 2.6 g/L, sodium carbonate 20 g/L in the electroplating solution g/L, sodium citrate 50 g/L, and sodium lauryl sulfate 0.1 g/L) for 5 min, and the current density was 3 A/dm ³ , and the activated brass sheet was placed in In the energized electroplating solution, heat in a water bath at 50 °C for 20 min. During the deposition process, ferrous phosphate solution was added to the electroplating solution (to make the final concentration of ferrous phosphate in the electroplating solution 5 g/L, and the pH of the electroplating solution was maintained at 8.5), and the Under the action of ultrasonic vibration at a frequency of 50 kHz and stirring at a rate of 10 r/min, a deposited multi-component Ni-Mo-W alloy coating was obtained. After the obtained coating was dried to remove moisture, it was kept in a vacuum heat treatment furnace at 400°C for 2 hours, and then cooled to room temperature with the furnace, and then removed by breaking the vacuum to obtain a multi-component Ni-Mo-W alloy coating on the surface of the brass substrate.

Table 1 shows the content changes of chemical components Mo, Ni, and W in Ni-Mo-W coatings prepared with different concentrations of sodium tungstate and sodium molybdate.

Table 1 Content changes of chemical components in Ni-Mo-W coatings prepared with different concentrations of sodium tungstate and sodium molybdate

It can be seen from Table 1 that as the concentration of sodium tungstate in the electroplating solution increases, the W content in the coating increases, while the Mo and Ni contents in the coating decrease slowly. This is because the higher the concentration of sodium tungstate, the higher the content of sodium tungstate on the surface of the nickel anode, the easier it is to obtain electrons, and react with H to be reduced, so that more W atoms can be deposited on the cathode , and solid solution into Ni atoms. At the same time, when the content of sodium tungstate remains unchanged, the content of Mo in the coating increases with the increase of sodium molybdate content. Combining Figures 3 and 4, it can be seen that the nanohardness of the sample increases with the content of W and Mo elements, which is due to the significant solid solution strengthening effect of Mo and W elements. At the same time, the hardness of the multi-component Ni-Mo-W coating prepared by the phosphate system in Comparative Example 1 is significantly lower than that of the multi-component Ni-Mo-W coating prepared by the sulfate system in Example 3 under the same composition ratio.

Table 2 shows the grain size of Ni-Mo-W coatings prepared at different heat treatment temperatures.

Table 2 Grain size of Ni-Mo-W coatings prepared at different heat treatment temperatures

It can be seen from Table 2 that in the range of 25-500 °C, the higher the heat treatment temperature, the larger the grain size of the microstructure, and the higher the crystallinity of the grain of the coating structure. It can be seen from Figure 5 that as the heat treatment temperature increases, the hardness of the sample generally decreases slowly, but between 300 and 400 °C, there is a process of increasing hardness, and the elastic modulus is basically the same. Combined with the morphology analysis in Figure 6, it can be seen that the grain size of the coating itself is relatively large, and after heat treatment, the grains grow up, and relatively coarse grains are obtained. According to Holpech's formula, the grain size increases, the yield strength decreases, and the strength and hardness decrease. However, between 300 and 400°C, the increase in the grain size of the coating is small, and the phenomenon of grain boundary relaxation often occurs, which leads to the increase of the hardness of the coating in this temperature range.

Based on the above analysis, the W element content in the multi-component coating is controlled at about 4 at%, and the vacuum heat treatment is carried out at 400 °C, so that the Ni-based coating with the best comprehensive mechanical properties can be obtained.

Other embodiments of the invention will be readily apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present invention, these modifications, uses or adaptations follow the general principles of the present invention and include common knowledge or conventional technical means in the technical field not disclosed in the present invention . The specification and examples are to be considered exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It should be understood that the present invention is not limited to what has been described above, and various modifications and changes can be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

Claims (9)

1. A method for improving mechanical properties of a multi-element Ni-based alloy coating by element doping and heat treatment is characterized in that the crystal grain size of the coating is reduced by doping W, mo element, and the internal stress of the coating is reduced by a certain heat treatment process, so that the obtained alloy coating has excellent comprehensive mechanical properties; the specific operation is as follows:

1) Polishing the metal substrate to smooth the surface of the metal substrate, degreasing the surface of the metal substrate by using a degreasing agent, ultrasonically cleaning the surface of the metal substrate, and activating the surface of a brass sheet to remove an oxide layer;

2) Performing direct current deposition while heating the treated metal substrate in an electroplating solution in a water bath to prepare a deposition-state multi-element Ni-Mo-W alloy coating; in the electrodeposition process, adding a certain amount of sulfate solution into the electroplating solution, and stirring and mixing;

3) And carrying out vacuum heat treatment on the deposited plating layer to obtain the multi-element Ni-Mo-W alloy plating layer.

2. The method for improving the mechanical property of the multi-element Ni-based alloy coating according to claim 1, wherein the metal substrate of step 1) is brass sheet; the ultrasonic cleaning time is 5 to 25min.

3. The method for improving the mechanical property of the multi-element Ni-based alloy coating according to claim 1, wherein the activation treatment in step 1) is soaking in dilute hydrochloric acid or dilute sulfuric acid with a volume fraction of 5-15% until the surface oxide skin is completely dissolved and the internal metal is exposed.

4. The method for improving the mechanical property of the multielement Ni-based alloy coating of claim 1, wherein the electroplating solution in the step 2) contains 20 to 120 g/L of nickel sulfate, 5 to 30g/L of sodium tungstate, 5 to 20g/L of sodium molybdate, 2 to 10 g/L of ammonium chloride, 5 to 60g/L of sodium carbonate, 30 to 150g/L of sodium citrate and 0.02 to 0.25 g/L of sodium dodecyl sulfate, and the pH value is 5~9.

5. The method for improving the mechanical property of the multielement Ni-based alloy coating according to claim 1, wherein the temperature of the water bath heating in the step 2) is 40-70 ℃ and the time is 5-35 min.

6. The method for improving the mechanical properties of the multi-Ni-based alloy coating according to claim 1, wherein the DC current density of the DC electrodeposition in the step 2) is 1 to 4A/dm ³ The deposition time is 2 to 30 min.

7. The method for improving the mechanical properties of the multi-Ni-based alloy coating according to claim 1, wherein the amount of the sulfate solution added in step 2) is converted into the final concentration of the sulfate solution in the electroplating solution of 0 to 20 g/L; the sulfate is one or more of ferrous sulfate, manganese sulfate, cobalt sulfate and copper sulfate.

8. The method for improving the mechanical property of the multielement Ni-based alloy coating according to claim 1, wherein in the step 2), a magnetic stirrer with an ultrasonic emission function is adopted for stirring and mixing, ultrasonic vibration is carried out at the frequency of 40 to 60kHz, and stirring is carried out at the speed of 5 to 15 r/min so as to be uniform.

9. The method for improving the mechanical property of the multi-element Ni-based alloy plating layer according to claim 1, wherein in the step 3), the vacuum heat treatment is carried out at 300 to 500 ℃ for 30 to 300 min, and then the multi-element Ni-based alloy plating layer is cooled to room temperature along with a furnace and taken out after vacuum breaking.

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