Improved Sinter-Hardenability of Prealloyed Fe-Cr-Mo Steels by Extra-Fine Nickel Additions

摘要

Extra-fine nickel (XFNi) powder was added to powder formulations based on prealloyed Fe-1.5Cr-0.2Mo, while XFNi and copper were admixed to a blend of Fe-1.5Cr-0.2Mo and Fe-0.5Mo in order to obtain a hybrid diluted PM steel (Fe-0.75Cr-0.35Mo) with admixed Ni and Cu. Parts with three different thicknesses were compacted from these blends at constant green density and then sinter-hardened at three different cooling rates. Extra-fine Ni additions were shown to clearly improve the sinter-hardenability of these PM steels. The density and mechanical properties increased significantly with admixed Ni content, while the properties of the hybrid diluted steel, which contained half the chromium, were either equal or superior to the base alloy. The properties generally increased with cooling rate irrespective of part thickness. The results of this investigation clearly show the potential of XFNi for improving the properties of PM Fe-Cr-Mo steels most effectively at lower cooling rates.