Nominally Equivalent Powders for P/M Steels: Analysis of Response to Sintering and Differences at Various C Content

Abstract

Globalization enables P/M part makers to choose powders from different sources. Raw materials produced by a given process and having equal chemical composition are supposed to be equivalent. The differences in sintering behavior, in industrial equipment, have been investigated on P/M steels obtained from four diffusion-bonded powders (Fe + Ni + Cu + Mo) on atomized iron base, at the same alloy contents. Two levels of carbon and two sintering conditions have been investigated. Dimensional changes, C content, hardness, microhardness pattern, universal hardness, fractal analysis, pore features, microstructure features, and rupture strength have been compared, to characterize different raw materials. An index of homogeneity of microstructures, based on a specific statistical approach, does not agree completely with observed microstructures and pore feature. The results show that the claimed equivalence is not confirmed by experimental data. Analyses of microhardness and microstructure distributions seem powerful tools to rate the real equivalence of so claimed powders. P/M part makers may use the proposed approach to assess detectable differences on performances among powders that are declared as “true” substitute, so confirming or contradicting any even not negligible cost difference. The comparison methods here described and applied can also help powder producers to improve the suitability of their products to sintering processes.