Study On Microstructure And Process Of Calorization Based On Pure Copper By Thermal Spraying

In modern industry manufacture,high temperature oxidation and heat corrosion are main reason of inactivity of facilities and parts working at high temperature. Oxidation-resisting property of metals relies on oxidation film property forming on metals. Al is the first elements which can generate stable,compact and excellently-protecting oxidation film.Because oxidation and heat corrosion occur on surfaces,in this paper electric arc spraying is used to add Al or Al alloy layer on copper matrix to improve its oxidation and corrosion resisting properties.Effect of parameters on inter-permeating of Cu and Al layers is analyzed through adjusting heating time,insulation time and layer thickness.Feasibility of Cu-layer protecting experiments is demonstrated by heat-temperature oxidation and corrosion experiments on pure Cu pieces and sprayed pieces,in order to research self-diffusion and inter-diffusion mechanism between atoms of layer and matrix in high temperature condition,SEM,EPMA and X-rays diffraction methods are used to analyzed alternation of layers' structure and formation of aluminized diffusion layer as well as diffusion rules and interaction between different elements.The results showed:when heating between 800 and 900℃,Al element in the layer diffused to Cu matrix,and Cu element did reversely.Aluminized diffusion layer formed finally composed of intermetallic compound Cu₉Al₄ andα-Cu solid solution.calorization layer composed of surface layer and inside diffusion layer,whose combination was excellent.In the course of heat spraying,molten drops were over -hot and oxide fully in the air,which were flatted and formed laminated structure when stroked on pieces surfaces at a high rate.calorization of Cu atoms in the matrix into Al layer formed surface calorization layer,which preserved oxidation and holes of original layers.Diffusion of Al atoms into matrix formed compact diffusion layer.In the same condition of diffusion treating,the thicker the Al layer and the longer the heating time,the thicker the formed calorization layer and the more the average Al content.Due to high content in the diffusion, the ability of supplying adequate Al atoms insured excellent bonding with matrix and contributed to formation of continuous protective Al₂O₃ film.