Lean alloys in PM: From design to sintering performance

Abstract

Low alloy sintered steels with an optimised content of alloying elements require the use of promising candidates such as Mn and Si, which can provide improved properties with minimum contents at a lower and less volatile price. The introduction of these alloying elements in the form of a master alloy powder prevents, to some extent, the oxidation and allows a proper ‘tailoring’ of its composition to accomplish particular goals. In this sense, low melting point alloys are especially interesting since they provide the formation of a liquid phase that enhances sintering and promotes the homogeneous distribution of alloying elements within the compact. In this work, the product developing process of master alloys containing Fe–Mn–Si is described from the theoretical design to the sintering performance. The effects of the liquid phase (produced by the added master alloys) are studied by differential thermal analysis and dilatometry. Moreover, to depict the behaviour of the liquid phase during heating, interrupted sintering experiments under high cooling rates were carried out. The results reported allow us to conclude that diffusion of carbon seems to be beneficial for lowering the melting temperature of the alloying particles, and the fact that the master alloys studied can dissolve part of the iron base particles has been shown to be beneficial for wetting.