Influence of Metallurgical Parameters on Wear and Impact Characteristics in High Chromium Manganese Irons

Abstract

Nickel chromium irons such as Ni-hard of different grades (high chromium iron) are being employed as wear-resistant materials in thermal power generation applications in view of their excellent inherent material characteristics. They are being deployed in bull ring segments, orifice, rolls, MPO, liners, etc., in thermal power plants and other engineering industries. But, these materials being brittle fail to withstand transient load. To overcome this problem, manganese is added to chromium iron to improve its impact characteristics apart from being wear resistant. In this context, the erosion and abrasion properties affected by metallurgical features are considered important from the point of enhancing its impact energy, without much sacrificing the wear resistance. Considering these aspects, high chromium manganese irons have been prepared in grey cast iron metal mould of section size of 24 mm, followed by heat treatment. The erosion, abrasion and impact energy have been studied using jet erosion, rubber wheel abrasion and drop weight impact test setup for varying manganese content in the range of 5, 10 and 15%. It is very much evident from the metallurgical investigations involving light microscopy that the least Mn content sample (5% manganese content) shows the highest wear resistance, whereas on the other hand, the highest manganese addition of 15% exhibits highest impact energy. The hardness and the metallurgical features support these findings as one could visualize the phases and carbide morphological features getting transformed during the heat treatment process, thus favouring the abrasion, erosion and impact properties. These results have been compared and analysed with the results obtained from high chromium iron samples.