Crack behavior and characteristics of laser clad layer with powder mixture of CO-based alloy and WC

Abstract

A powder mixture of Stellite-6 and tungsten carbide (WC) in the range of 0wt%∼47wt%WC with a normal multi-layer cladding and novel multi-layer cladding were deposited on mild steel (JIS-SM400B) plates by a 2.4kW cw CO2 laser. In the normal multi-layer cladding, the WC weight fractions at each layer are constant In the novel multi-layer cladding, the WC weight fractions at each layer are varied by controlling the disk rotation speed of the feeder. The microstructure, hardness and wear resistance of the clad layer were investigated by an X-ray diffractometry, energy dispersion spectroscopy (EDS), scanning electron microscope (SEM), laser microscope, Vickers hardness tester and wear tester. According to the analyzed results, the microstructure of the clad layer belonged to a hypoeutectic structure. In addition, the undissolved tungsten carbides dispersed in the matrix of the Co-based alloy. The Vickers hardness increases with the increase of WC weight fraction. Using a WC constant weight fraction in the third layer, the clad layers of normal multi-layer cladding and novel multi-layer cladding have almost same wear resistance. On the other hand, to decrease the crack sensitivity of clad layer, the influence of a preheating temperature and WC weight fraction in the normal multi-layer cladding and novel multi-layer cladding on the crack sensitivity was investigated comparatively. As the result, the cracks of clad layer made with the powder mixture of Stellite-6 and WC belonged to a quasi-cleavage fracture type crack. In the novel multi-layer cladding with gradual increase of WC particles clad at three subsequent layers shifts the critical amount of WC at which cracking appears to the higher level, or that it reduces the required preheating temperature.A powder mixture of Stellite-6 and tungsten carbide (WC) in the range of 0wt%∼47wt%WC with a normal multi-layer cladding and novel multi-layer cladding were deposited on mild steel (JIS-SM400B) plates by a 2.4kW cw CO2 laser. In the normal multi-layer cladding, the WC weight fractions at each layer are constant In the novel multi-layer cladding, the WC weight fractions at each layer are varied by controlling the disk rotation speed of the feeder. The microstructure, hardness and wear resistance of the clad layer were investigated by an X-ray diffractometry, energy dispersion spectroscopy (EDS), scanning electron microscope (SEM), laser microscope, Vickers hardness tester and wear tester. According to the analyzed results, the microstructure of the clad layer belonged to a hypoeutectic structure. In addition, the undissolved tungsten carbides dispersed in the matrix of the Co-based alloy. The Vickers hardness increases with the increase of WC weight fraction. Using a WC constant weight fraction in the thir...