预热温度对钢轨表面激光熔覆贝氏体涂层的影响

Effect of Preheating Temperature on Laser Clad Bainitic Coating on Surface of Steel Rail

利用激光熔覆技术在不同预热温度的钢轨基板表面制备了贝氏体涂层。利用光学显微镜(OM)、扫描电镜(SEM)观察了涂层的微观组织,应用X射线衍射仪研究了涂层中的物相分布,分析了涂层的显微硬度。结果表明:基板预热温度在280~380℃内,随预热温度的升高,涂层的原始奥氏体晶粒尺寸先增大后减小,预热温度为320℃时,涂层的奥氏体晶粒尺寸最粗大;原始奥氏体晶粒越粗大,相变后形成的贝氏体组织越少,马氏体/残留奥氏体(M/A)组织越多;M/A组织对涂层的硬度影响较为显著,基板预热320℃的涂层M/A组织最多,硬度最大。

The bainitic coatings were fabricated on the surface of steel rail substrate by laser cladding technology at different preheating temperatures.The microstructure of the coating was observed by metallographic microscope (OM) and scanning electron microscopy (SEM).The phase distribution of the coating was examined by X-ray diffraction (XRD).The microhardness of the coating was studied.The results show that the original austenite size of the coating increases firstly and then decreases with the increase of preheating temperature,when the preheating temperature is 280 ℃ to 380 ℃.The austenite grain size of the coating is the biggest when the preheating temperature is 320 ℃.The thicker the original austenite grain,the less bainitic structure appears after the phase transformation,in addition,the more the martensite/retained austenite (M/A) structure.The hardness of the coating is obviously affected by M/A structure,while the coating has the most M/A structure and the biggest hardness when the substrate preheating temperature is 320 ℃.