High Wear Resistance of White Cast Iron Treated by Novel Process: Principle and Mechanism

Abstract

Based on microstructure desired, a novel process is proposed to treat Fe-2.4C-12.0Cr (mass pct) white cast iron balls, that is, destabilizing heat treatment following multicycle quenching and sub-critical treatment (De-MQ-Sct) process, and such a complex process is simply performed by alternate water quenching and air cooling. For comparison, the white cast iron balls also were treated by conventional normalization (NOR) process and Oil-quenching process, respectively. The partitioning of carbon from martensite to retained austenite during De-MQ-Sct process promotes the interaction between carbide precipitation and martensitic transformation, while this interaction is a unique effect only produced by multicycle quenching linking destabilizing and sub-critical treatments, which leads to more and finer secondary carbides and more carbon-enriched austenite in De-MQ-Sct sample than those in NOR or Oil-quenching sample. The average hardness of 60 HRC and impact toughness of 12.6 J/cm2 are obtained in De-MQ-Sct white cast iron balls, which are much higher than those in NOR and Oil-quenching ones. The wear behaviours measured by pin-on-disk wear tests indicate that the weight loss of De-MQ-Sct sample is only about one third of the NOR sample and one half of the Oil-quenching sample. Microstructural characterization reveals that high wear resistance related to hardness and toughness of the De-MQ-Sct balls are mainly attributed to the considerable fine secondary carbides and stable carbon-enriched retained austenite.