Research On The Technology Of Electroless Ni-p Plating And Heat Treatment On A Contrate Gear Being Made With Magnetic Iron

A contrate gear of clutch transmission mechanism being made with magnetic iron is a part of automatic throttle control system in an aircraft. In the work, there is friction and relative motion between it and other parts. In order to improve the surface hardness, the contrite gear will be electroless plated by nickel phosphorus alloy and heat-treated in the surface, thus avoiding mechanical failure caused by wear. And then, the quality of the product can be guaranteed, because the surface hardness increases. Using orthogonal design in this project, the different levels of the test parameters have been made, which include coating thickness, temperature and time of heat treatment. Through the experiment and the actual making of production, the process parameters of coating thickness of 10μ m~15μ m, heat treatment temperature of 400℃, the holding time of 1h are determined. Using this method, the surface hardness of the parts can be up to 800(HV0.1) above. As proved by the corrosion resistance and durability of the vibration test, the parts meet the requirement of product. By using X-ray diffraction(XRD) method to carry on the phase structure and phase composition analysis, and using scanning electron microscope(SEM), energy dispersive X-ray analysis(EDAX) method microstructure and precipitated phase composition were analysed. These results indicate that, after heat treatment, the electroless Ni-P plating has changed from amorphous to crystalline, and precipitation of Ni3 P phase has caused the hardness improved. Therefore, the wear resistance of parts has been improved. At the same time, the influence of electrical iron and stainless steel substrate on the properties of nickel phosphorus alloy coating was compared, and the mechanism is preliminary analysed.