GB1214428A - Method of producing dispersion strengthened nickel-chromium alloys - Google Patents

Abstract

1,214,428. Sintered Ni-Cr dispersion hardened alloys. SHERRITT GORDON MINES Ltd. April 21, 1969, No.20296/69. Headings C7D and C7F. A wrought oxide dispersion strengthened Ni alloy containing 10-35% Cr is made by depositing the Cr on a wrought, dense, shaped Ni matrix containing the oxide dispersion and homogenizing the deposited Cr in the Ni matrix by heating at 1095‹-1320‹C in a protective atmosphere such as hydrogen. The dispersed oxide which may be ThO 2 , YO 2 or CeO having a particle size of 10- 50m, microns is mixed with Ni powder of 0À2-0À5 micron size to form 2-4% volume. The powder mixture may either be pressed to a green compact of 60% density e.g. by isostatic compaction and then hot worked to a dense body or formed directly into a dense body by extrusion. The Ni-oxide body is then preferably cold worked and annealed in repeated cycles such that the area reduction is less than 20% per cycle, and annealing is at 1205‹C. The dense sintered body is then chromized either by electro-plating or by pack diffusion at 1095‹- 1320‹ C in a pack of Cr and Al 2 O 3 . Following chromizing, homogenizing heat treatment is then carried out at 1095‹-1320‹C in hydrogen. The micro structure of the Ni matrix is retained in the finished Ni-Cr alloy. Co, W, Mo, Nb and Ta may be included in the composition either by mixing with the Ni and oxide powders prior to processing or introduced later by vapour deposition.