Fabrication,Microstructure And Properties Of Fe-Cr-C Laser Cladding Layers On Cr5 Steels

Backup roll,a large-sized shaft part in mill,supports work roll or intermediate roll,which prevents the flexure deformation of work roll resulting in poor quality of slab.The quality of backup roll affects the yield and quality of rolling strip directly.Backup roll has a large size,long manufacturing cycle and high production costs and its invalidation leads to great economic losses to Steel Enterprise.If the backup roll is repaired and remanufactured by laser cladding technology,its service life can be greatly prolonged and the cost will be reduced.As the key management part to iron and steel enterprises,the backup roll has high requirements on performance and stability.Also it is difficult to remanufacture.So far,comparatively mature technologies such as embedding,surfacing and so forth are used to remanufacture the backup roll.The use cost of Fe-Cr-C iron-based alloys is low and the system has low sensitivity to crack during cladding.In this paper,laser cladding technology was adopted to prepare Fe-Cr-C iron-based alloy cladding layer with different microstructures and properties by optimizing the parameters of the laser process and adjusting the content of carbon and chromium in the alloy powder.X-ray diffraction(XRD),transmission electron microscopy(TEM),optical microscope(OM),scanning electron microscope(SEM)and energy dispersive spectroscopy(EDS)were used in present paper to analyze the microstructure,component and phase composition.The hardness was tested by micro-hardness test.The friction and wear test was used to test the wear resistance of the cladding layer and the mechanical property testing machine was used to test the bending strength of the cladding layer.The optimum parameters of laser cladding are as follows:laser power is 1700 W,scanning speed is 4 mm/s,powder feed rate is 18.9 g/min and lap rate is 30%.Laser cladding layers are metallurgical bonding with matrix.The organization has a low defect density.With adding a series of carbon content in Fe-Cr-C alloy powders,different hardness of cladding layers were obtained.When the carbon content increases,the intergranular structure decreases gradually,while the martensite content,hardness,wear resistance all increase obviously.The hardness of A2 cladding layer is between 450?500 HV,which meets the repair hardness requirement of working layer of target support roller.By changing the chromium content in Fe-Cr-C alloy powders,cladding layers with different hardness were prepared.With the increase of chromium content,the intergranular structure lessens by degrees,and the martensite content,hardness,wear resistance increase synchronously.The hardness of B15 cladding layer is between 450?500 HV,which achieves the repair hardness requirement of working layer of target support roller.What's more,the wear resistance of B15 is superior to A2.