COMPUTER-ASSISTED OPTIMIZATION OF COBALT-BASE ALLOY COMPOSITIONS

Cobalt-base hard metals are known for their wear and corrosion resista nce and also for their ability to retain hardness at elevated temperat ures. Considering the matrix of these alloys it can be predicted that (a) the performance against corrosive media will improve when the Cr c ontent is increased, (b) a higher W content will be advantageous becau se of its solid solution strengthening effect, and (c) care has to be taken in the course of liquid phase sintering to avoid unwished-for ca rbides and/or intermetallic phases, because these would be detrimental with respect to mechanical properties of the alloys. To locate ranges for optimal matrix and carbide compositions thermodynamic calculation s with CHEMSAGE were carried out on the basis of recently published da ta which were improved by a new optimization routine. A series of phas e diagrams was calculated and the optimal compositions of alloys were derived. Furthermore, calculated transition temperatures and phase com positions of some selected alloys compare reasonably with published ex perimental results.