High temperature corrosion behaviour of HVOF sprayed WC-CrC-Ni coatings

Effect of burnishing on HVOF coated boiler steel against hot corrosion in actual boiler environment

“…The low porosity value of the selected HVOF coating also contributes to its superior hot corrosion performance. The low porosity value of this coating as reported by Somasundaram et al [44] also contributes to its superior hot corrosion performance. Burnishing reduces porosity, improving hot corrosion resistance.…”

“…The fast production of oxides at the splat borders and inside open pores during early cycles may be responsible for the increased mass gain seen at these times [43]. Once formed, oxides may clog pores and splatter at the edges, preventing further admission of oxidizing species by serving as diffusion barriers [44]. This continuous condition of oxidation with increasing exposure time follows because the development of the oxide is confined to the surface of the material [45].…”

“…Chromium and cobalt oxides, coupled with cobalt–chromium (CoCr 2 O 4 ) and nickel-chromium (NiCr 2 O 4 ) spinels, may have hindered CoO diffusing activities by preventing its production [28,54]. After the first hours of exposure, chromium, and silicon oxides may have operated as a diffusion barrier, confining its presence to the scale–substrate interface [44,55]. The islands of aluminum at the scale/substrate interface that do not correlate to coating powder or substrate alloy may have formed due to aluminum powder amalgamation during polishing [56].…”

Tribological Behavior of Co-WC Composite Coatings

“…In recent years, metal matrix composite coatings reinforced with inert ceramic particles play an irreplaceable role in energy saving, material saving and environmental protection due to its excellent wear resistance [2][3][4][5]. The general methods for preparing ceramic composite coatings are high velocity oxygen fuel (HVOF) spraying [6,7], plasma spraying [8] and vacuum sputtering [9], etc. However, there are several limitations in the previous approaches such as the complicate technique and the high temperature.…”