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

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 results 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.