Influence of retained austenite on abrasive wear performance of bainitic steels

Abstract

Bainitic steels exhibit improved strain hardening and comparable ultimate tensile strength and hardness properties as compared to quenched and tempered steels giving bainite the possibility of replacing martensitic steel in certain wear susceptible components, e.g. earthmoving and mining equipment. The influence of retained austenite morphology and mechanical stability in abrasion-resistant bainitic microstructures generated in a medium C, high Si AISI 9260 is investigated in the present study. Evaluation of critical phase transformation temperatures and production of carbide free bainitic microstructures were performed using dilatometry. Hardness measurements, X-ray diffraction, and microscopy were employed to evaluate these heat treatments. The overarching goal of this work is to develop a scientific understanding of interrelationships between retained austenite in bainitic steels and wear performance evaluated with dry sand/rubber wheel wear testing. A correlation between lower austempering temperatures and higher hardness was observed due to both microstructural refinement, as well as a higher content of martensite. Wear results show a complex relationship between austemper temperature and wear resistance, suggesting a dependence on sample hardness, austenite content, and austenite morphology.