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为提高牙轮钻头的使用寿命,用20Ni3Mo代替20Ni4Mo钢,并采用930±10℃×6h的渗碳淬火工艺预处理后,再用液氮及其蒸发空间温度梯度制冷深冷处理。通过磨损试验和透射电镜观察TEM组织表明,深冷处理后,20Ni3Mo钢硬度提高72HRC,耐磨性提高89%,其组织为均匀马氏体、残余奥氏体和微细碳化物。残余奥氏体转变为马氏体及超微细碳化物的析出是提高20Ni3Mo渗碳钢硬度与耐磨性的重要原因。
In order to improve the service life of roller cone bit, 20Ni3Mo was used instead of 20Ni4Mo steel, pretreated with carburizing and quenching process at 930 ± 10 ℃ × 6h, and then cryogenic treated with liquid nitrogen and its evaporation space temperature gradient. The TEM microstructure of the 20Ni3Mo steel was improved by wear test and transmission electron microscope. The hardness of 20Ni3Mo steel increased by 72HRC and the wear resistance increased by 89%. The microstructure of the 20Ni3Mo steel was homogeneous martensite, retained austenite and fine carbides. Residual austenite into martensite and the precipitation of ultrafine carbides is an important reason to improve the hardness and wear resistance of 20Ni3Mo carburized steel.