Influence of La2O3 addition on nano indentation hardness and residual stress of Stellite 6 coating prepared by plasma cladding

One of the problems limiting the application of Stellite 6 coating is the residual stress resulting in cracks in the coating easily. In order to reduce the residual stress and increase the nano-indentation hardness, La 2 O 3 was added to Stellite 6 coating in this study, and the influence on the microstructure, nano indentation hardness and residual stress of the coatings were investigated by scanning electron microscopy (SEM) with energy dispersive spectrum (EDS), X-ray diffraction (XRD) and nano-indentation tester. Results indicate that the addition of La 2 O 3 leads to the phenomenon that the dendrite is partly transformed into the equiaxed grain, which results in the grain refinement. The nano-indentation hardness of coatings is improved, which is attributed to the fine-grain strengthening and dispersion strengthening effect of La 2 O 3 . With the addition of La 2 O 3 , the residual stress in coatings is decreased significantly. Especially, when the content of La 2 O 3 is 0.8 wt%, the nano indentation hardness increases by 1.31 times and residual stress decreases to 20 percent, compared with coating without La 2 O 3 .