铝合金Ni-Co-P/Si_3N_4镀层的化学复合镀制备及其硬度

Ni-Co-P/Si_3N_4 electroless composite plating and its hardness

针对铝合金硬度较低等缺点,采用化学复合镀方法在铝合金表面制备了Ni-Co-P/Si3N4镀层。通过正交试验,研究了铝硅合金基体化学镀Ni-Co-P/Si3N4镀层的工艺参数对镀层硬度的影响。得出镀液pH值、硫酸钴/(硫酸镍+硫酸钴)物质的量比、氮化硅粉末含量、施镀温度对硬度的影响规律。发现:增大pH值以及镀液中氮化硅含量,保持硫酸钴/(硫酸镍+硫酸钴)物质的量比适中、升高施镀温度可以提高镀层硬度。此外,研究了热处理温度对镀层硬度的影响,发现:硬度随着热处理温度升高而增大,当热处理温度超过400℃时,硬度开始下降。

Ni-Co-P/Si3N4 composite coating on Al alloy is prepared by electroless composite plating in order to improve the minohardness of Al alloy.The influence of electroless plating process parameters on the micro-hardness of Ni-Co-P/Si3N4 coating on a hyper-eutectic Al-Si casting alloy is studied by an orthogonal experiment.The effects of process parameters,such as pH and mole ratio of Co 2＋/（Co 2＋ ＋Ni2＋）,Si3N4 concentration in electroless plating bath and plating temperature,on the micro-hardness of composite layer are obtained.It is indicated that the hardness of coatings can be increased by increasing pH,plating temperature,Si3N4 concentration and keeping mole ratio of Co2＋/（Co 2＋ ＋Ni2＋）moderate.Moreover,the influence of heat treatment on the micro-hardness of coatings is also investigated.It is found that the hardness of films increases with the heat treatment temperature rising below 400 ℃ but decreases when temperature is over 400 ℃.