铁基自熔合金等离子熔覆层的微观组织及强化机理研究

Microstructure and Strengthening Mechanism of Fe-based Alloy Powder Cladding Layer by Plasma Beam

采用金相显微镜（OM）、附带能谱的扫描电镜（SEM-EDS）、X射线衍射（XRD）技术及显微硬度分析手段研究了铸铁表面铁基自熔合金粉末等离子熔覆层的微观组织及强化机理.结果表明,采用等离子熔覆技术,铁基合金粉末可在铸铁表面获得与基体冶金结合良好、无裂纹的强化层.熔覆层微观组织主要由近似于六方形或板条状、U形、L形或H形的初生（Cr,Fe）7C3相及短杆状、小块状或颗粒状的（Cr,Fe）7C3共晶碳化物、α-（Fe,Cr）和Fe3C组成,熔覆层与基体界面为细小的共晶莱氏体组织.熔覆层显微硬度可达600～1200HV0.2,熔覆层中高硬度的（Cr,Fe）7C3相、Fe3C相的存在、大量Cr、Si溶质原子溶入基体引起的固溶强化和快速加热及快速冷却产生的细晶强化是熔覆层得以强化的主要原因.

The microstructure and strengthening mechanism of Fe-based alloy powder cladding layer by plasma beam heating are investigated by means of optical microscope （OM）, scanning electron microscopy with energy dispersive spectroscopy （SEM-EDS）, X-Ray diffractometer （XRD） and microhardness tester. The resuits show that Fe-based alloy powder cladding layer by plasma cladding technology can metallurgically bond with the cast iron substrate, and has no cracks. The cladding layer has a microstructure consisting of primary phase of （Cr,Fe）7C3, eutectic carbide （Cr, Fe）7C3, α-（Fe,Cr） solid solution and Fe3C. Primary phase （Cr, Fe）7C3 is approximately in hexagon,U, L, or H shape and eutectic carbide （Cr,Fe）7C3 is in short bar,small nubby,or particle. The fine eutectic ledeburite is formed on interface between cladding layer and substrate. The microhardness of the cladding layer can reach 600-1200HV0.2. The precipitation of hard carbide （Cr,Fe）7C3 and Fe3C in cladding layer, and the solid solution strengthening by large amount of Cr and Si supersaturated in α solid solution, and grain size strengthening by rapidly heating and solidification result in the strengthening of cladding layer.