Laser Cladding Of NiFeBSi Alloy Coating Enhanced By Nano-SiC

NiFeBSi alloy has not only larger thermal expansion coefficient,but also excellent erosion,intensity,rigidity,and plasticity;as a ceramic material,SiC has perfect rigidity,heat and electric conductivity,also can antioxidant while stays high temperature.Laser cladding metal matrix composites coating enhanced by ceramic,is widely researched.In this paper, NiFeBSi alloy coatings and composites coating enhanced by SiC are cladded on substrate 45^# steel surface,have good metallurgical bonding,and not diluted by substrate to reduce characteristics.Feeding style of cladding materials is presetting that spread powders of alloy and composites enhanced by SiC on substrate 45^# steel surface.Thickness of powders is about 0.8mm,and agglomerant is not used.Coatings are prepared on the surface of substrate 45^# steel by circular spot single-pass laser-cladding with high power flow CO₂ laser,circular spot with high energy model can make melting bath cool-down fast to get good mechanics and physical chemistry characteristics coatings.Process parameter is as follows:laser spot diameter isΦ3mm,power is from 2.0kW to 4.0kW,scan velocities are 3mm/s,6mm/så’Œ8mm/s respectively.The phase and microstructure of coatings are investigated by XRD and SEM;the hardness is tested by DMH-2LS and the wear resistance by CETR UMT-2.NiFeBSi alloy coatings with different composition are composed of FeNi₃,γ-(Fe,Ni),α-(Fe,Ni) and Ni₂Si.FeNi₃,γ-(Fe,Ni) are FCC structures andα-(Fe,Ni) is BCC structure. Microhardness and wear resistance of coatings are better than substrate.Microhardness and wear resistance of coatings tend to decrease,andα-(Fe,Ni) tends to increase as composition of Ni decreases.As a result of laser irradiation has a greater condenser depression,makes the coatings solidify rapidly.Eutectoid reaction has no time to be occurred in order that a large number ofγ-(Fe,Ni) are reserved.NiFeBSi alloy coatings with different process parameter are investigated.Dilution,microhardness and wear resistance of coatings tend to decrease, composition of FeNi₃ andγ-(Fe,Ni) both tend to decrease,andα-(Fe,Ni) tends to decrease as power increases.Dilution tends to decrease,microhardness and wear resistance tend to increase then decrease,composition ofα-(Fe,Ni) tends to Multiply,and composition of FeNi₃ andγ-(Fe,Ni) both tend to decrease significantly as scan velocity increases.Dilution,microhardness and wear resistance of coatings tend to decrease,composition of FeNi₃ andγ-(Fe,Ni) both tend to decrease,andα-(Fe,Ni) tends to decrease as energy density increases.Wear resistance is best as energy density is 0.5k(kJ/mm²),then decreases slightly.NiFeBSi alloy coatings with different wt.%SiC doped are composed of FeNi₃,γ-(Fe,Ni),α-(Fe,Ni),NiC_x,Fe₃C,Fe₇C₃,and (Fe,Ni)₂₃C₆.Composition of FeNi₃ tends to decrease gradually,α-(Fe,Ni) andγ-(Fe,Ni) both tend to decrease significantly as composition of nano-SiC doped increases.SiC ceramic phase is not discovered by XRD in coatings and resolves during the cladding process.Coatings of composites coating enhanced by nano-SiC improve microhardness and wear resistance of substrate 45^# steel surface.Microhardness and wear resistance of coatings tend to increase significantly as composition of SiC doped increases.Brittle deformation and cracks are discovered on wear track surface.