HVOF spraying MCrAlY coatings on single crystals with various sand blasting forces

Sand blasting and high-velocity thermal spray processes such as HVOF can produce residual stresses in superalloy substrates which further makes large influence on the the microstructure development in the residual stress zones. In this paper, different sand blasted single crystal substrates were prepared (with no or slight or heavy blasting force). The substrates were then used to make MCrAlY coatings by trying various spraying distances in HVOF processes. After a typical vacuum heat treatment, microstructure in the substrates and coatings were analyzed. It was found that the sand blasting process had significant influence on the size of residual stress zone. HVOF spray also produced stresses into the single crystal. Elemental interdiffusion between the substrate and coating took place in the vacuum heat treatment. How the sand blasting and HVOF spray affected the microstructure evolution near the substrate-coating interface was discussed.