Analysis on microstructure and friction wear performance of chromium carbide/Ni₃Al composite surfacing layer

Microstructure of chromium carbide reinforced Ni₃Al-based matrix composite coating prepared by argon tungsten-arc welding was investigated with optical microscope,scanning electron microscopy(SEM),electron probe micro-analysis(EPMA) and X-ray diffraction(XRD).The wear performance of the coating and cast iron of piston ring were tested by a Pinon-Disc tribometer.The results indicated that the Ni₃Al-based matrix was formed during welding,a large number of fine carbide particles such as Cr₃C₂ and Cr₇C₃ dispersed in it;The particle of Cr₃C₂ in welding wire was dissolved and re-precipitated during hardfacing.The re-precipitation of chromium carbide particle contains Fe,Ni elements and forms strong metallurgically bond with Ni₃Al-based matrix.Diffuse distribution of chromium carbide particles and Cr solid-solution in Ni₃Al-based matrix,makes the surfacing layer with higher hardness.The hardfaceing layer shows excellent dry friction wear resistance and its friction coefficient is 0.23,lower than 0.39 which is the friction coefficient of piston material of vermicular graphite cast iron.The wear rate of hardfaceing layer is only 43 percent of vermicular graphite cast iron.