Modeling of the influence of admixing and prealloying on the optimisation of compressibility and sinter-hardenability of steel powders

The automotive industry applies pressure on the PM industry to produce components with superior mechanical properties at minimum cost. In this regard, sinter-hardenable powders are particularly well suited since they allow direct quenching of components at the end of the sintering cycle, thus eliminating the extra steps required for heat treating. This paper presents the results of the modeling of the influence of admixing and/or prealloying on the optimization of compressibility and hardenability of sinter-hardenable steel powders. A first design of experiments (DOE) was used to optimize the chemical composition and to study the interactions between prealloyed elements (Nickel, Chromium, Molybdenum and Manganese) and admixed elements (Nickel, Chromium, Manganese and Copper) on hardenability and compressibility. A second DOE was generated based on the results obtained in the first series. Results show that among all of the examined alloying elements, only prealloyed nickel, chromium and molybdenum had a significant effect on compressibility and hardenability. Moreover, within the range of concentrations under study, the optimum sinter-hardenable powder had the following (prealloyed) chemistry: 1.5 wt-% Ni, 0.55 wt-% Cr and 1.25 wt-% Mo.