Influence of Various Heat Treatments on Hardness and Impact Strength of Uddeholm Balder: Cr-Mo-V-Ni Novel Steel Used for Engine Construction

Abstract

The construction of an engine requires optimized geometry and superb material properties in various environments. Tensile and yield strength are not the only parameters essential to consider. Hardness, impact toughness, and ductile-brittle transition temperature (DBTT) are also crucial. In this paper, Balder, Chromium-Molybdenum-Vanadium-Nickel steel with low impact toughness attested is considered. It contains both high Nickel and high Vanadium content, a rare combination among iron-based alloys. This study aims at proving that conventional heat treatment can improve its impact toughness while maintaining hardness level, exceeding its to-date performance. Steel’s exact elemental composition was checked, and material samples’ hardness and impact toughness were measured. Four heat treatments were proposed, then hardness and impact toughness were measured again. It was established that impact toughness over three times higher than marketed (57.3 J against 17 J) can be achieved with simultaneous 2 HRC points (from 46.4 HRC to 48.4 HRC) rise in hardness. Achieved parameters place examined alloy at the high-ranking position among similar steels. Occurrence of temper embrittlement was avoided. Notably, the ductile-brittle transition was not observed in any sample.