Effect of Double Austenitization and Pre-Annealing Heat Treatment on the Microstructural and Mechanical Properties of QT 41Cr4 Steel

Abstract

In this study, the effect of double austenitization and pre-annealing heat treatment on the final microstructure concerning changes in hardness, strength, impact toughness and hardenability characteristics of 41Cr4 steel has been examined in comparison with conventional quenching-tempering treatment. The microstructural changes were characterized by an optical microscope (OM) and scanning electron microscope (SEM), and also the variations in austenite grain sizes and carbide sizes were estimated with the Image J program. The results indicated that precursor microstructures formed with quenching and also subcritical annealing tailored the prior austenite grains and carbides in a manner of improving the strength and toughness without loss in hardness and ductility. 776 MPa yield strength and 30 J Charpy impact energy were obtained in conventional quench-tempering settings, and the corresponding values for double austenitization treatment were 886 MPa and 71 J, and 830 MPa and 34 J for pre-annealing treatment, respectively. Grain size reduction and modification of carbides in tempered martensite microstructure with the applied pre-heat treatments resulted in advanced Charpy impact energies including cryogenic test circumstances and room temperature strength values.