施镀条件和热处理对铝合金Ni-P-SiO_2复合镀层微观结构及显微硬度的影响

Effects of Plating Conditions and Heat Treatment on Microstructures and Microhardness of Electroless Plating Ni-P-SiO_2 Coating on Aluminum Alloy

目的提高Ni-P镀层的硬度。方法在化学镀Ni-P过程中添加SiO2微粒,形成Ni-P-SiO2复合镀层,研究施镀温度、微粒添加量和镀后热处理温度对复合镀层微观结构及硬度的影响。结果复合镀层含非晶结构Ni和SiO2相。随施镀温度的升高及SiO2微粒添加量的增加,镀层表面变得均匀、致密且硬度升高,显微硬度最高达355HV;当施镀温度超过80℃,微粒添加量超过10 g/L时,镀层表面均匀性变差,硬度下降。经热处理后,镀层向晶态转变,热处理温度达到300℃时开始析出Ni3P相,镀层的显微硬度随热处理温度的升高而升高。结论当施镀温度为80℃、微粒添加量为10 g/L时,所得复合镀层的性能较为优异,热处理可进一步提高复合镀层的硬度。

Objective In order to improve the hardness of single eleetroless plating Ni-P coatings, SiO2 particles were incorpo- rated into the plating to form Ni-P-SiO2 composite coating. Methods The effects of plating temperature, concentration of SiO2 parti- cle and temperature of heat treatment on the structure and hardness of the deposits were analyzed. Results It was found that amor- phous Ni and high content of SiO2 phase were detected in the composite coating. With the increase of plating temperature and con- centration of SiO2 particle, the coating became more homogeneous and dense, and exhibited increased hardness till 355HV. How- ever, the coating surface was rough and porous, and the hardness decreased when the plating temperature was above 80 ℃ and the particle concentration was higher than 10 g/L. After heat treatment, the coating was transformed to crystalline and the coating hard- ness was raised. The Ni3 P phase appeared when the coating was heated at 300 ℃ for 1 h. Conclusion When the temperature was 80 ℃ and the concentration of SiO2 particle was 10 g/L , the performance of composite coating was the best. The microhardness of coating raised with the increasing temperature of heat treatment.