Abstract
Effects of boron and carbon contents on tensile properties at 760°C were investigated for Ni-base PM-alloys with compositions fixed for main components (content of gamma prime phase : 65%). The obtained results were compared with those of cast alloys with the same composition of main component.
When specimens were prepared by powder-metallurgical procedures-HIP-consolidation of alloy powder, superplastic forging of it, or additional heat treatment on either of the former two-, Yield Strength (YS), Ultimate Tensile Strength (UTS) and Elongation to fracture (EL) were improved by addition of a small amount of boron (say 0.02%) except for the case of as-forged products. However, EL deteriorated by further increase in boron content, although UTS and YS remained almost unchanged. YS, UTS and elongation deteriorated, when carbon content increased from 0.02% to 0.20%. The properties of the HIPed or forged products were improved by an appropriate heat treatment.
When specimens were prepared by casting, trend seen for as-cast products was not much different from what was seen for as-HIPed ones. After the same heat treatment, however, the properties abruptly deteriorated. EL vanished and UTS decreased by more than 30%.
