Effects of Carbide Size and Ni-plated Powder on the Microstructural and Mechanical Properties of HVOF-sprayed WC-12Co Coating

Abstract

In this paper, high velocity oxygen fuel (HVOF) sprayed WC-12Co coating was investigated according to two variables that can influence the extent of decarburization such as different carbide size by mechanical milling and the Ni-plated powder. Identification of each phase and phase quantitative analysis were conducted by X-ray diffraction (XRD) and general microstructure was investigated by field emission scanning electron microscopy (FE SEM) on each feedstock powder and resultant coating. In order to distinguish WC and W2C phases through the image contrast in accordance with phase atomic weight, back scattered election (BSE) mode in FE SEM was used on each WC-12Co coating. In addition of these results, based on the crystal structure data, transmission electron microscopy (TEM) analysis and electron backscatter diffraction (EBSD) phase map analysis were implemented to identify positions and characteristics of each phase, and then nano-scale mechanical properties of each phase were measured by nano-indentation on the same position with EBSD phase map. Finally, micro-indentation of each coating was conducted to know general mechanical properties of each coating. After implementing all experiments, effects of two variables in HVOF-sparyed WC-12Co coating are elucidated by the correlating between micro-scale mechanical properties of each coating, microstructural distribution and nano-scale mechanical properties of each phase.