HIGH STRENGTH POWDER-METALLURGY COBALT-BASE ALLOYS FOR USE UP TO 650 degree C.

The first part of the work concerns P/M grades containing (in wt. %) 10 to 15%Ni, 20%Cr, 10%Mo and up to 1. 8%C, strengthened mainly by solid-solution effects and precipitation of carbides. The second part deals with grades containing 16%Cr, 3 to 5% Mo, 5%Ti and less than 0. 1%C strengthened by solid-solution effects and precipitation of the ordered f. c. c. gamma prime -Co//3Ti intermetallic compound. Ultimate tensile strengths up to 1850 MN/m**2 at room temperature and 1350 MN/m**2 at 650 degree C (1200 degree F) were obtained in the gamma prime -Co//3Ti strengthened alloys. Relationships between microstructures and mechanical properties are discussed in terms of the powder characteristics, and the extrusion and subsequent hot-working and aging conditions.