Peening Effect of Thermal Spray Coating Process

The present study investigated the influence of grit blasting, feedstock powder, and thermal spraying technology on performance near the surface on the substrate’s side. The experimental results show that both the grit-blasting process and thermal spraying process harden the substrate, and microhardness on or near the surface was noticeably increased. Grit blasting created deformed regions next to the surface of the substrate and interface between entrapped grits and substrate. Initial equiaxed grains in the deformed regions were elongated and spirally oriented surrounding impact spots. There were no visible changes in microstructure caused by thermal spraying, and the elongated grain regions remained in the coated substrate. Substrate hardening was attributed to grit blasting and associated heating due to flame rather than powder particle impacting during thermal spraying, thus feedstock powder and individual thermal spray technology had no influence on the hardening.