Designs and preparation of advanced HVOF-PVD duplex coating by combination of HVOF and arc ion plating

Advanced HVOF-PVD duplex coatings were produced on the medium carbon steel by combinations of High Velocity Oxygen-Fuel (HVOF) and arc ion plating. The microstructures and mechanical properties were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) in association with mechanical property measurement. The results show that the duplex coating are composed of an inner NiCr-Cr3C2-based HVOF-sprayed layer mainly consisted of γ-NiCr and Cr3C2 phases, and an outmost PVD-AlCrN layer containing fcc-AlCrN phase. Duplex coatings reveal more excellent wear resistance when compared to the HVOF-sprayed coating. The improved wear resistance is mainly related to the outmost AlCrN layer with more excellent wear resistance in comparison to the HVOF-sprayed coating against WC ball. The AlCrN layer deposited on NiCr-75 wt.% Cr3C2 duplex coating reveals higher wear resistance than that of the AlCrN layer deposited NiCr-30 wt.% Cr3C2 duplex coating. The improvement of wear resistance is mainly associated to its higher surface hardness, load capacity and bond strength. The main wear mechanisms of the duplex coatings are adhesive and oxidation wear, whereas the ones of the single HVOF-sprayed NiCr-Cr3C2-based coating are adhesive wear as well as spalling and chipping wear.