Effect of austenitizing temperature on microstructure, strength and toughness of gear and bearing steel with ultrahigh strength and high heat-resistant

Abstract

A new class gear and bearing steel with ultrahigh strength and high heat-resistant has excellent strength and toughness. The steel was austenitized at different temperatures, combined with a variety of mechanical property tests and micro-analysis techniques to study the changes in microstructure and mechanical properties of the steel. The results show that M6C carbides are undissolved, then the impact energy and fracture toughness decrease respectively when the steel is austenitized at 1060 ℃; the M6C carbides are dissolved, then the impact energy and fracture toughness increase respectively when the steel is austenitized at 1080-1100 ℃. There is little change in tensile strength and plasticity, and the specified plastic elongation strength decreases slightly with the increase of austenitizing temperature, when the steel is austenitized at 1060-1100 ℃. The initiation and propagation of crack is accelerated by M6C carbides, resulting in decrease in toughness. The steel has an excellent combination of strength and toughness when the steel is austenitized at 1080-1100 ℃, and the tensile strength is not less than 2000 MPa, the proof strength of specified plastic extension is not less than 1800 MPa, and the fracture toughness is not less than 100 MPa·m1/2.

Keywords

• gear and bearing steel with ultrahigh strength and high heat-resistant
• austenitizing tempe-rature
• microstructure
• strength and toughness
• m6c carbide