硼铸铁激光表面淬火的显微组织及耐磨性

Microstructure and Wear Resistance of Laser hardening Layer on Boron Cast Iron

采用光学显微镜、电子显微镜和Ｘ射线衍射仪研究了激光表面淬火处理硼铸铁硬化层的显微组织及激光处理前后硼在铸铁中的存在形式。在滑动磨损试验机上测量了激光硬化层的耐磨性。研究结果表明，硼铸铁铸态组织为珠光体＋片状石墨＋微量游离铁素体＋角状化合物（包括Ｆｅ３Ｐ、Ｆｅ３（ＰＢ）及Ｆｅ２Ｂ）。激光淬火处理后组织超细化，熔凝层为树枝状初晶（Ｍ＋Ａ’）和树枝间层片状共晶（变态莱氏体即Ｍ＋Ａ’＋Ｆｅ３Ｃ或Ｆｅ３（ＣＢ））。固态相变层为隐针马氏体、残留奥氏体及未溶解的石墨与硼化物。硼铸铁激光淬火处理后硬度及耐磨性显著高于未经激光处理的硼铸铁和灰铸铁。

The microstructure of the laser hardening layer on boron cast iron and exsisting form of boron in the cast iron before and after laser surface hardening were examined by optical microscope,transmission electron and X ray diffractometer.The wear test was carried out in a sliding wear device.The experimental results show that the microstructure of boron cast iron in the casting state consists of pearlite matrix graphite in flake ,a little ferrite and promontoroied compound with Fe 3P,Fe 3(PB) and Fe 2B.The microstructure with dendritic (M+A) nad interdendritically laminal transformed ledeburite(M+A+Fe 3C or Fe 3(CB)) is formed in the melted layer and the microstructure with cluster of acicular martensite,retained austenite,undissolved graphite and boride is formed in the solid transformed layer after laser processing.The hardness and wear resistance of the boron cast laser hardening are higher than those of the grey cast iron and the boron cast iron in the casting state.