Wire-are-sprayed nickel-aluminum is widely used in the aircraft industry for dimensional restoration of worn parts and as a bond coat for thermal barrier coatings and other top coats. Some repair applications require thick coatings, which often result in lower bond strength, A mechanism being investigated to explain this decrease in bond strength is the free edge effect, which includes both coating residual stresses and coating thickness. The layer-removal method was used to determine experimentally the residual stresses in wire-are-sprayed nickel-aluminum coatings of different thicknesses, Bond strength evaluations were performed using an improved ASTM C 633-79 test specimen, Finite-element analysis and fracture mechanics were used to investigate the effects of coating thickness and residual stress state on coating bond strength.
