Microstructure of single track fiber laser cladding with wire feeding by side

Laser cladding was performed on the surface of stainless steel with wire feeding by side. To obtain an optimal combination of process parameters, orthogonal test was used to determine the influences of laser power(P), scanning velocity(v_s) and wire feeding speed(v_w) on the cross-section geometry, aspect ratio and dilution rate of cladding track. The results show that the stable and smooth cladding track can be obtained when the combination of process parameters are P=2 000 W, v_s=4mm/s, and v_w=20 mm/s. Grain morphology of the cladding track from the binding to the surface are planar crystal, cellular crystal, columnar dendrites, equiaxed dendrite, steering dendrites. The microstructure of laser cladding track is composed of γ austenite and residual δ ferrite, and the δ ferrite distributed in the austenite grain boundaries or between dendrites with the vermicular, skeletal and lathy morphologies. The average microhardness of the cladding track is about 195 MPa near to the one of substrate(207 MPa), which is evenly distributed, but the microhardness of heat affected zone(178 MPa) is lower than the one of substrate.