Fe based (W,Ti)C EAS and WC-12Co HVOF sprayed coatings: microstructure, mechanical properties and micro-scale abrasion performance

The application of cermet material coatings deposited by thermal spray techniques such as high velocity oxy-fuel (HVOF) has not ceased expanding to many industrial fields, especially for protection of mechanical components and industrial parts against wear and corrosion. Recently, electric arc spray process (EAS), using cored wire as feed-stock, has been considered a step over HVOF technology thanks to its low effective cost and high deposition rate. In this work, the microstructure, hardness and abrasive wear performance of FeCrNiSiB-(W,Ti)C coatings deposited by EAS were compared with WC-12Co coating deposited by HVOF process. The microstructure of the feed stock material and deposited coatings as well as the mechanical properties of the deposited coatings were characterized by scanning electron microscopy/energy dispersive x-ray analysis (SEM/EDAX), x-ray diffraction (XRD) and micro-hardness measurements. The tribological properties were evaluated at room temperature in a micro-scale abrasion device. As expected, coatings exhibited different morphologies, i.e. WC-12Co HVOF coating displayed a more homogeneous and dense microstructure, with low degree of carbide decomposition; whilst, FeCrNiSiB-(W,Ti)C EAS coatings showed an heterogeneous microstructure with more pronounced phase transformation. W-C phase on the EAS coating was dissolved in the metallic matrix which leads to the formation of new and complex carbides. The wear rate of Fe based EAS coatings was just 1.9 times higher than the one of HVOF coating. Despite of this, Fe based-(W,Ti)C EAS coating offers a potential solution for surface protection of parts as compared to HVOF coating, due to the lower production costs of the former. (paper)