Strengthening Mechanism of Ti(C_yN_1-y) Particle on Metal Matrix Composite Layer by Laser Cladding

Fe-based composite layer with Ti（C_yN_1-y） particles was prepared on the surface of cast steel by laser cladding process using transverse CO₂ laser beam as inducing heat source.The microstructures and strengthening mechanism of laser clad layer were analyzed by means of optical microscopy（OM）,X-ray diffraction（XRD） instrument,scanning electron microscopy（SEM） and transmission electron microscopy（TEM）.The microhardness of the layer was measured by using microhardness meter.The results show that the surface quality of laser clad layer which is composed of bonding metal matrix and second phase particle Ti（C_yN_1-y） homogeneously dispersed is fairly good.The newly formed particles Ti（C_0.3N_0.7）and Ti（C_0.2N_0.8）come into being by some new chemical combination reactions,and most of Ti（C_yN_1-y） particles are irregular.The microhardness of laser clad layer distributes within HV_0.2 800～900.Microanalysis of the clad layer shows that the strengthening mechanism of the layer includes fine grain strengthening,dispersing strengthening of hard particles and solid solution strengthening.