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.