In this study, two high-entropy alloys (HEA), FeCoCrNiAl (HEAL) and FeCoCrNiMn (HEAM), were deposited on IN718 substrates by the high velocity air fuel (HVAF) technique at gun traverse speeds (GTS) of 600, 800, and 1000 mm/s. Lower GTS resulted in relatively higher levels of porosity and surface roughness due to consolidation of weakly bonded particles with inadequate flattening however with the advantage of higher deposition efficiency. Higher speeds produced dense coatings, but with lower deposition efficiency. Raman spectroscopy indicated that the oxide content in the coatings decreased as the GTS increased. The microhardness showed an increase of up to ∼23% at 1000 mm/s compared to 600 mm/s for both coatings. Scratch tests demonstrated higher cohesion and adhesion strength as gun traverse speed increased. Though HEAL showed higher hardness compared to HEAM, the latter showed better cohesion and adhesion. Coatings at 1000 mm/s exhibited lower friction and a reduced wear rate compared to those at 800 mm/s. At room temperature, wear is more pronounced and abrasive, while at elevated temperatures, wear became progressively oxidative. The wear rates of both HEA coatings deposited at higher GTS demonstrated reductions of ∼20% and 11%, respectively. Alumina in HEAL and manganese-chromium oxide complexes in HEAM play a key role in determining the wear rates at higher temperatures.
Babu et al. (2026) studied this question.