EFFECT OF CHARGE FRACTIONAL COMPOSITION ON HIGH-SPEED STEEL POWDER SINTERING

The fractional composition of gas-atomized high-speed steel R6M5K5 is studied for its effect on the main features of activated sintering of compacts. A mixture consisting of nickel powder and 30% (wt.) boron is used as an activating addition. It is estabished that a reduction in average particle size increases shrinkage after sintering, but the dep endence of compact shrinkage on fractional composition is different fo r monodispersed and polydispersed compositions. The maximum size of po wder particles for polydispersed compositions has little effect on shr inkage, whereas in the case of monodispersed mixtures there is a marke d increase in compact density after sintering with a reduction in part icle size. There is a marked increase in density providing closed poro sity (90-93%) with a sintering temperature of 1200-degrees-C, whereas in order to achieve a similar density in the mixture without activator the sintering temperature should be at least 1230-degrees-C.