TC4钛合金表面化学镀Ni-P合金耐磨层研究

Electroless Ni-P Wear-Resistant Coating on TC4 Titanium Alloy

摘要:

利用化学镀方法在TC4钛合金表面成功制备结合力良好的Ni-P合金耐磨层，研究了提高镀层结合力的方法，结合SEM、XRD、EDS等现代物理分析方法分析了不同温度热处理后镀层的组织结构，从而建立不同热处理温度、镀层结构与镀层硬度和耐磨性能的关系。结果表明：二次浸锌活化方法和热处理能显著提高镀层与基体的结合强度，经600 ℃热处理后镀层结合力达到35 N。基材的硬度HV为3780 MPa，磨损量为9.6 mg，镀态镀层的硬度HV为5760 MPa、磨损量为7.7 mg。随着热处理温度升高Ni3P相增多，该相的弥散分布使镀层硬度增加，最高硬度HV达到9790 MPa，但400 ℃后硬度降低，这是由于Ni3P相随着热处理温度的继续升高而发生偏聚，使弥散强化程度下降；镀层的磨损量随着热处理温度的升高而减小，说明耐磨性能随着热处理温度的升高而增强，600 ℃热处理后，虽然镀层晶粒长大、粗化及镀层硬度降低，但此时镀层晶格的完整性最佳，镀层塑性和韧性提高，所以耐磨性能最好

Abstract:

Ni-P alloy coatings with good adhesion and wear resistance were prepared on the surface of titanium alloy TC4 substrate using an electroless plating method. The structures of coatings after heat treatment at different temperatures were investigated by means of SEM, XRD and EDS. Furthermore, the relationship of different heat treatment temperatures, coating structure, coating hardness and wear resistance was established. The results show that the combination of double zincating and heat treatment can significantly improve the adhesive strength in the coating/substrate interface, and the adhesion of the coating reaches 35 N after heat treatment at 600 °C for 1 h. Hardness HV and wear loss of the substrate are 3780 MPa and 9.6 mg, respectively, while the hardness HV and the wear loss of the coating as plated are 5760 MPa and 7.7 mg, respectively, which indicate that electroless Ni-P coating can enhance hardness and wear resistance of TC4 titanium alloy. With the increase in temperature of heat treatment, Ni3P phase increases. The hardness shows higher values in the presence of Ni3P phase with highly-dispersed distribution, reaching the highest of 9790 MPa. Further increase in temperature results in the segregation of Ni3P phase and slowdown of dispersion degree, suggesting the hardness reduction. Wear loss of the coating decreases with increasing heat treatment temperature, revealing the wear resistance increases with the rise of heat treatment temperature. After heat treatment at 600 °C, despite the bigger grains and lower hardness of the coating, the best crystal integrity is produced, and the plasticity and the toughness of the coating are increased, so the coating shows the best wear resistance.