GCr15钢轴承内套圈滚道不规则碳化物的成因

对锻造、球化退火、淬回火等工序后GCr15钢轴承内套圈组织中的碳化物形貌进行观察,结合热膨胀试验和热力学分析,研究二次碳化物的溶入、析出与长大行为,分析了带尖角大颗粒不规则碳化物形成的原因。结果表明:G C r 15钢轴承内套圈在较低温度辗挤成形时,其滚道表层合金元素偏析区中已析出的二次碳化物发生破碎,导致滚道表层组织中出现带尖角的大颗粒不规则碳化物;球化退火过程中轴承内套圈滚道表层破碎的不规则颗粒状碳化物长大并变得圆整,淬火加热时这些大颗粒碳化物部分溶入奥氏体而重新呈现棱角。轴承内套圈滚道表层出现不规则碳化物的条件包括滚道表层存在较严重的合金元素偏析区,偏析区中析出大块二次碳化物。

Formation Mechanism of Irregular Carbides in Raceway of GCr15 Steel Bearing Inner Ring

The carbide morphology in the GCr15 steel bearing inner ring structure after forging,spheroidizing annealing,and quenching and tempering was observed.Combining with thermal expansion tests and thermodynamic analysis,the dissolution,precipitation and growth behavior of secondary carbides were studied.The forming reasons for large irregular carbides with sharp corners were analyzed.The results show that the secondary carbides precipitated in the alloy element segregation zone of the raceway surface of GCr15 steel bearing inner ring during rolling and forming at a lower temperature were broken,resulting in the appearance of large irregular carbides with sharp corners in the raceway surface structure.During the spheroidizing annealing process,the broken irregular granular carbides on the raceway surface of the bearing inner ring grew up and became round,and these large carbides partially dissolved into the austenite matrix during quenching heating,resulting in the reappearance of edges and corners.The conditions for the appearance of irregular carbides on the raceway surface of bearing inner ring included the presence of a serious alloy element segregation zone on the raceway surface,and the large secondary carbides precipitated from the segregation zone.