| 摘要 |
PURPOSE:To form fine grains only in the surface layer of an r' precipitation hardening type austenitic alloy and to improve the resistance to steam oxidation by subjecting said alloy to a soln. heat treatment then cold working the surface by polishing, shot blasting, etc., and subjecting again the alloy to the soln. heat treatment and aging treatment at the temp. around the specific temp. thereby forming the crystal grains at a specific grain size value or above. CONSTITUTION:An r' precipitation hardening type austenitic alloy which is, for example, a blade material for an ultra-super critical pressure steam turbine is subjected to a soln. heat treatment. The surface of the alloy is cold-worked by polishing, shot blasting, etc. and is further subjected again to the soln. heat treatment and aging treatment at about 800 deg.C to attain >=6 crystal grain size. The cold-worked layer is regulated to >=40 micron thickness. Fine grains are thus formed only on the surface layer of the material and the resistance to steam oxidation is improved. |
