Process for the manufacture of a workpiece from a creep-resistant alloy

Claim 1

A process for the manufacture of a workpiece, having high creep strength at high temperatures, from a high-nickel alloy which contains a metal oxide as a hardening dispersoid, comprising the following steps: (a) preparing randomly shaped particles of a mechanically alloyed, dispersoid containing metal powder comprising a metallic alloy and a metal oxide dispersoid by bonding metallic powders and fine metallic oxide particles through a mechanical alloying process, (b) subjecting said particles of mechanically alloyed metal powder to a hot or warm rolling process, effecting non-work hardening deformation, thereby deforming said randomly shaped particles into elongated flaked shapes such that the original volume of the particles increases by no more than a factor of 5.0 and the degree of deformation, ε, is greater than 0.1, where ε=|ln(h.sub.f /h.sub.o)|, in which h o , denotes the mean particle diameter before the rolling operation and h f denotes the mean particle thickness after the rolling operation, and wherein the deformation rate ε=de/dt is maintained within the limits such that 10.sup.15 (m.sup.-2)<ε/D<10.sup.20 (m.sup.-2) ε being defined as ##EQU3## v=2 πRν=Peripheral speed of the rolls, in m/s R=radius of the rolls, in m ν=rotation speed of the rolls, in revolutions per second and D is the diffusion coefficient, represented by the equation ##EQU4## T=Temperature, in Kelvin m=unit of length, in meters s=unit of time, in seconds (c) encapsulating the resulting metal powder flakes in a metal container, and (d) subjecting said metal powder flakes to thermal-mechanical temperature by an isostatic hot-pressing operation, and then (e) immediately subjecting said treated metal powder flakes to an annealing thermal treatment operation to obtain the finished coarse grained workpiece.