Influence of Heat Treatment on Microstructure and Mechanical Properties of Ni-Mo-W Ternary Coating
The ternary Ni-Mo-W electroplating coating was prepared by using sodium tungstate as tungsten source and sodium molybdate as molybdenum source.NiMo10W20 samples prepared with sodium tungstate concentration of 20 g/L and sodium molybdate concentration of 10 g/L were heat-treated at 300℃,400℃ and 500℃,respectively.The results show that,when the content of tungsten in the plating solution increases gradually,the content of tungsten in the coating also increases,while the content of molybdenum decreases,the coating grain size at 500℃ heat treatment is raised obviously.X-ray diffraction(XRD)test on the Ni-Mo-W alloy coating find that,the coating crystallizes best at 500℃,but the W content has no significant effect on the coating.According to the change curves of the nano-indentation hardness and the elastic modulus,the hardness of the NiMo10W20 sample coating decreases slowly as the heat treatment temperature increases.However,at the heat treatment of 300-400℃,the hardness is improved.As the W content in the coating increases,the coating hardness increases slowly.Therefore,the addition of Mo and W elements can increase the thermal stability and high-temperature mechanical properties of the nickel-based coating.
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