Characteristics of multilayer laser cladding using powder mixture of Co based alloy and vanadium carbide

Abstract

The powder mixture of Co based alloy (Stellite 6) and vanadium carbide (VC) in the range of 0–56 wt-%VC fraction with a constant chemical composition multilayer cladding (CCCMLC) and functionally gradient material multilayer cladding (FGMMLC) were deposited on stainless steel (SUS304) by a 2·4 kW CW CO₂ laser and powder feeder. In the CCCMLC, the VC weight fractions at each layer are constant. In the FGMMLC, the VC weight fractions at each layer are varied by controlling the disc rotation speed of the powder feeder. To decrease crack sensitivity of the clad layer, influence of preheating temperature and VC weight fraction using the CCCMLC and FGMMLC on the crack sensitivity was investigated comparatively. As a result, in the FGMMLC with gradual increase in VC particles, clad at three subsequent layers shifts the critical amount of VC at which cracking appears to be the highest level, or it reduces the required preheating temperature, namely, the crack sensitivity of the clad layer using FGMMLC is lower than that using CCCMLC. On the other hand, the microstructure, Vickers hardness and wear resistance of the clad layer were investigated by an X-ray diffractometer, energy dispersion spectroscopy (EDS), scanning electron microscope (SEM), laser microscope, wear tester and hardness tester. Microstructures of the clad layer were classified into two types, hypoeutectic structure and hypereutectic structure. The wear resistance of clad layer made by CCCMLC and FGMMLC has been almost the same.