U.S. Pat. No. 4,050,133 to Cretella is directed to a method for refurbishing turbine vanes including a plasma spray coating process performed in an argon atmoshpere. The vanes include cooling passages in the interior portion.
U.S. Pat. No. 4,251,599 to McCormick teaches a process for plasma spray coating a metal body while cooling the surface with an external blast of inert gas. Weatherly et al U.S. Pat. No. 4,095,003 is directed to a duplex coating method comprising plasma spraying followed by heat treatment in an inert atmosphere.