Abstract
Effect of cryogenic treatment on microstructure, hardness, and wear resistance of high Cr-C tool (D6) steel has been studied, in comparison with effect of conventional quench-temper treatments on those properties. Cryotreatment includes austenitizing, quenching in hot oil, immediate cooling of steel down to -78 or -180˚C, and keeping the samples at one of those temperatures for 6 or 24 hours. The results show that retained austenite decreases in microstructure and submicron carbides precipitate in matrix of steel after cryotreated samples, in relative to those after conventional quench-temper treatment. Wear resistance in cryotreated samples significantly increases in comparison of conventialy treated samples, however, hardness variation is moderate. Hardness and wear resistance increases as time and/or cooling increases during cryotreatment. It is revealed that increasing holding time in cryogenic environment from 6 to 24 hours improves wear resistance by 23%, however decreasing temperature of cryogenic environment from -78 to -180˚C provides only 4% improvement in wear resistance. Increasing velocity of wear disk increases wear resistance, whereas, increasing applied load decreases wear resistance of steel. In general, wear resistance of D6 steel after cryotreatment is significantly superior to those properties in D6 steel after conventional quench-temper treatment.
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