The aqueous corrosion and wear responses of HVOF-deposited TiC-Ni3Al, WC-Co, and WC-CoCr coatings on AISI 4130 steel substrates

In prior studies, TiC-Ni3Al cermets have shown an excellent combination of corrosion and wear resistance in comparison to WC-Co, while exhibiting <50 % of the mass. Consequently, it is attractive to assess these materials in coating form. The aqueous corrosion and wear performance of TiC-Ni3Al cermet coatings, deposited by high-velocity oxy-fuel (HVOF) thermal spray onto AISI 4130 steel substrates, is examined in the present work. Two powder feedstock formats were investigated. The first is a conventional agglomerated and sintered powder, which is then compared to a micro-composite powder feedstock fabricated via a novel gelation technology. The HVOF coatings were subsequently examined in terms of their microstructure, corrosion, and wear behaviours. The potentiodynamic polarisation responses of the cermet coatings were assessed in a simulated sea water environment (deaerated H2O with 3.5 wt% NaCl). The reciprocating sliding wear responses were also examined, against a WC-Co counter-face sphere. The post-corrosion and worn surface morphologies were subsequently investigated with optical microscopy, scanning electron microscopy, and associated energy dispersive X-ray analysis, with focused ion beam milling used to evaluate the wear track cross-sections. The TiC-Ni3Al HVOF sprayed cermet coatings demonstrate a combination of high wear and corrosion resistance in comparison to conventional WC-Co and WC-CoCr cermet coatings that were also HVOF deposited and tested under similar conditions.