Improving the wear resistance of M41 steel by nitrogen alloying and ESR

AISI M41 high-speed steel (HSS) is considered as a super-hard tool steel due to high hardness level (65–70 HRC). Nitrogen alloying of AISI M41 HSS produces marked solid solution hardening and precipitation strengthening in addition to an improvement in pitting resistance. The mechanical properties in general, and wear resistance in particular, are strongly affected by the steel cleanliness and the status of non-metallic inclusions in steel. For this reason tool steel should be subjected to a secondary refining process. In this work, the wear characteristics of AISI M41 HSS were investigated. The effect of nitrogen alloying and electroslag refining (ESR) of this steel grade were considered. Both conventional and nitrogen alloyed grades were melted in open air induction furnaces and then remelted under three different compositions of calcium fluoride-based flux in an ESR machine. The wear behaviour of the resulting steels, for both conventional and nitrogen-alloyed grades before and after ESR, was monitored. The addition of nitrogen improves markedly the wear resistance of AISI M41 HSS. This improvement depends on the total nitrogen content and is independent on the form of the nitrogen constituent. The ESR process improves markedly the wear resistance of both conventional and nitrogen-alloyed grades.