Abstract: A method for repairing an environmental protective coated article portion of a gas turbine engine article made of a Ni base superalloy including Cr and at least about 6 wt. % total of Al and Ti comprises removing the coating, exposing the article portion to a reducing mixture of gases including, by weight, greater than 6% up to about 20% hydrohalogen gas with the balance principally hydrogen gas, and preferably about 10-15 wt. % hydrogen fluoride gas. Exposure is at a temperature in the range of about 1600.degree.-2000.degree. F. for a time, greater than about 2 hours, and preferably about 2-10 hours, sufficient to remove from within the article portion metal sulfides, Al, Ti, oxides of Al or Ti, or their combinations. Then the article portion is recoated. One form relates to weld repairing the article portion by removing Al or Ti or both to a depth up to about 0.003".

Abstract: A method for improving oxidation resistance life of a metallic coating deposited on a metallic alloy including boron treats the alloy to reduce the boron prior to depositing the coating. The article provided by using a diffusion coating method has a diffusion zone between the coating and the alloy substrate characterized by the substantial absence of boride needles traversing the diffusion zone from the coating into the alloy.