A Study of the Influence of Niobium on Sintering and Properties of MIM 440C Stainless Steel Manufactured by Pre-alloy and Master Alloy Routes

摘要

The use of Metal Injection Moulding (MIM) continues to expand to cover an increasingly varied rangeof components across a multitude of advanced applications. One of the most versatile alloys currentlyused in MIM is 440C martensitic stainless steel as it offers a combination of high hardness and goodcorrosion resistance. These characteristics make the alloy suitable for applications includingautomotive engine parts, medical instruments and a range of machine tool components. Achievingreproducible properties and consistent hardness requires close control of carbon levels in particular.There are a number of variants on 440C in use today: some with enhanced carbon levels to achievehigher hardness and some with additions of niobium (Nb), which are claimed to increase the sinteringprocess window for the alloy. In this study, we examine the sintering behaviour at differenttemperatures of 440C and 440C+Nb made by pre-alloy and master alloy routes. Differences inhardness and mechanical properties are discussed with reference to chemistry and microstructures ofsintered parts.