Formation and tribological behavior of AC-HVAF-sprayed nonferromagnetic Fe-based amorphous coatings

Nonferromagnetic Fe-based amorphous coatings (AMCs) were fabricated by an activated combustion-high velocity air fuel (AC-HVAF) thermal spraying system. The microstructure, hardness, and nanoindentation of the AMCs were investigated. In particular, the abrasive wear of the coatings was evaluated by a combination of nanoscratch and dry friction tests. The average wear volume of the Fe-based AMCs under dry friction is about one-fourth of that of the steel substrate, demonstrating the AMCs' superior wear resistance. Microcracks are observed near the micropores and intersplat regions because of the weak bonding force among the atoms and the brittleness of the AMCs. The dominant wear mechanism of AMCs under dry friction is revealed to be oxidative wear accompanied with delamination wear arising from crack formation and propagation. Nanoscratch results indicate that the Fe-based AMCs exhibited lower penetration depth and higher elastic recovery than the 304 stainless steel substrate. The scratch length dependence of wear volume during nanoscratch follows a power law with a power exponent of ~ 6.2, instead of the modified Archard equation.