Residual Stress Characteristics of High Velocity Oxygen-Fuel MCrAlY Coatings.

High velocity oxygen-fuel (HVOF) system in air has been established for producing the coatings that are extremely clean and dense. It is thought that the HVOF sprayed MCrAlY (M is Ni, Co or Fe) coatings can be applied to prevent oxidation and corrosion in the hot section of gas turbines. Also, it is well known that thicker coatings can be sprayed for improving the residual stress in comparison with any other thermal spraying system. However, the thermal and mechanical properties of HVOF coatings have not always been clarified.In this paper, the thermal and mechanical properties of MCrAlY coatings were measured in both cases of as sprayed and heat treated coatings. From the results, it is confirmed that the thermal and mechanical properties of HVOF MCrAlY coatings could be improved by a diffusion heat treatment up to the level of vacuum plasma sprayed MCrAlY coatings. On the other hand, the experimental results suggest that the residual stress of HVOF coatings is decreased by the shot-peening effect in comparison with the vacuum plasma sprayed coatings.