Abstract: Unwanted recrystallization during heat treatment of a directionally solidified nickel alloy single crystal casting is prevented by chemical milling the part before heat treatment. Removal of a layer of as little as 0.013-0.050 mm thick, less than two percent of the part thickness, has been found effective.

Abstract: Methods for heat treating cast, nickel base superalloy articles are described. According to the invention, the articles are heated to progressively higher temperatures greater than the gamma prime solvus temperature and less than the incipient melting temperature. The incipient melting temperature is increased due to homogenization of segregate phases, while at the same time, the gamma prime goes into solution. The rate at which the temperature is increased closely approximates the rate at which the incipient melting temperature increases due to homogenization.

Abstract: A heat treatment is described for producing a desired microstructure in Hastelloy Alloy X components which have small diameter, closely spaced, laser pierced holes therein. The heat treatment produces a small grain size and discontinuous carbide morphology in the component prior to the hole piercing operation, which reduces the propensity for cracking which has been found to be associated with the hole piercing operation. After the piercing operation, the component is heat treated again to increase the grain size and produce a microstructure which provides the optimum balance of creep strength and fatigue strength.

Abstract: Residues accumulated during use are removed from the small interior cavities of superalloy airfoils by a process which includes exposing the interior of the part to an aqueous solution of 20-45% potassium hydroxide at a pressure of 10.4-24 kPa (150-350 psi) and temperature of 150.degree.-235.degree. C. (300.degree.-450.degree. F.) for about 20 hours, followed by water blasting using a pressure greater than about 14 MPa (2,000 psi). Unless the part is kept continuously wet between the first and second steps, the second step will not be effective.