Study On Coating Of Ni-P/nano Diamond Electroless On Aluminum

In order to make the aluminum and its alloys successfully used in the aerospaceindustry, we need to give them special surface treatment. With the electroless platingtechnology’s improving, surface treatment’s technology are gradually mature. Thereappeared many excellent properties’ multi-alloy plating. But the coating which iscombined with the aluminum alloy can not reach the desired requirements.By the introduction of nano-diamond particles, this article invented Ni-P alloycoatings. This study has investigated the impact of the bath temperature, pH value,nano-diamond concentration and stirring speed to the multi-alloy plating organization.And we used EDS, SEM, XRD and other means of detection to analyse multi-alloyplating’s surface morphology, micro-hardness, abrasion resistance, bond strength. Atthe same time, the article introduced multi-alloy plating’s changes of the surfacemorphology and wear resistance before and after the heat treatment.Results:(1) the three technological parameters (salt concentration, pH value andtemperature) have different influence to the electroless plating, Ni-P coating hardnessand bonding force. Among them temperature effects most, followed by the pH value,and the main salt concentration is less affected. Within a certain range, the hardness ofthe coating will increase as the plating temperature and pH increases.(2) After orthogonal optimize, the basis bath parameters is: temperature85°C,pH value5, the main salt25g/L. And the coating has the highest hardness, the bestbinding capacity, good wear resistance, uniform coating surface and the coatingperformance is the best;(3) stirring speed change affects the adsorption of nano-particles in the substratesurface, also affects the surface morphology and friction coefficient of the compositecoating. Experiments showed coating surface morphology is the best when the stirringspeed is300r/min.(4) nano-diamond’s concentration increase will add the nano-diamond particle’scontent of the substrate’s surface. And made the multi-alloy plating’s coating surfacebecomes more dense and uniform. But if higher than6g/L, due to thenano-diamond covered the substrate surface catalytic active center, multi-alloyplating’s density falls. (5) Ni-P multi-alloy plating reaches the maximum hardness after400°C heattreatment. If temperature was increased successively, Ni3Pand Ni phase grain growth,grain coarsening caused the decrease of hardness. Thus after heat treatment at400°C,Ni-P/nano-diamond composite coatings’ are mainly organized by the crystallineNi3P, Ni and inlaid nano-diamond particles, and nano-diamond particles do notparticipate in the crystallization process of the coating.(6) Under the same conditions, nanodiamond multi-alloy plating which has beenheat-treated has much smaller friction coefficient, stable friction performance and1/6wearing capacity, showing good wear resistance.