Production and Characterization of Carbide-Free Cast Bainitic Steels with Two Different Mn Contents

Abstract

Carbide-free bainitic steels (Fe-0.8C-1.7Si-0.9Al-1.2Cr-0.2Mo) with two different Mn concentrations (1.4 and 2.0 wt.%) are produced via conventional sand-casting technique. Computational JmatPro calculations were performed to evaluate the present phases and transformation temperatures. Austempering and deep cryogenic heat-treatment are applied. The microstructural, mechanical and wear properties are investigated in detail and compared with those of traditional 100Cr6 bearing steel. With increasing Mn content from 1.4 to 2.0, the Ac1 and Ms temperatures decrease and the bainite nose shifts to longer times. The microstructures of studied as-cast bainitic steels are fully pearlitic, whereas the microstructures of austempered steels are composed of bainite and retained austenite. Ultrahigh hardness values (56-59 HRC) are observed for heat-treated steels which are comparable to those for 100Cr6 steels (59-61 HRC for quenched and tempered). Tempered 100Cr6 steels exhibit the best wear resistance with the lowest wear loss. In addition, austempered 1.4Mn and 2.0Mn steels show the best wear resistance among bainitic steels. Their wear resistance is comparable to that of tempered 100Cr6 steels.