Research On Laser Cladding Wear And Corrosion Resistance Layers On 45# Steel

Laser cladding use high energy laser beam to melt coating material and a thin layer base metal to form a kind of good metallurgical bonding surface coating. It was one of new techniques in the modern surface technique system that infinite development future and characteristic. Laser cladding layer has good properties Laser cladding technique is good for repairing and enhancing of work pieces. When laser cladding technique could improve properties of work pieces and lengthen their lift time. While corrosion resistance of laser cladding layers researches were not systemically investigated. Laser cladding also have widely use in industry of aerospace, automobile, metallurgy, petroleum, chemical industry and etc.Laser cladding layer on Ni60 and Ni60+WC alloys was made by CO₂ LASER on steel 45# substrate.The macro-morphology, microstructure, hardness, wear resistance and corrosion resistance were investigated. Properties of Ni60+WC and CeO₂ cladding layer on 45# substrate were also investigated.The result shows that Ni60 laser cladding layer has good surface quality. Cross section rise with interaction time and energy density increasing. But there was crack and role in Ni60+WC cladding layer. Adding rare earth elements could reduce these defects. The cladding layer mainly constituted byγ-(Ni,Fe), N_i3B, CrB, M₇C₃ and M₂₃C₆. New phases such as WC and CeB₂C₂ etc. precipitated because of the adding rare earth elements. SEM and EDS results showed that the coating is mainly composed by cladding zone, alloying zone and transition zone. Ni60 cladding zone is mainly composed by dendrites structure and block Cr-rich phase; alloying zone is mainly flat crystal structure and direction columnar crystal structure and transition zone has quenching martensite microstructure. Ni60 + WC coating contains a large number of snow like, block, graininess, needle-like and round morphology carbide. Adding rare earth element could refine micro-structure of cladding layer and reduce the number of carbides.Micro-hardness of Ni60 cladding (800HV) layer is about 3 times of 45# steel (300 HV). Micro-hardness of Ni60+ WC coating is about 1000HV, after adding CeO₂, it grows up to 1200 HV. Ni60 and Ni60 + WC laser cladding layer greatly improved wear resistance of 45# steel. Wearing mechanism of 45# steel is adhesive wearing, while wearing mechanism of laser cladding layer is mainly grinding abrasion. Laser cladding coating have compact microstructures and its crystals are fine. Defects and inclusions are reduced greatly after adding rare earth CeO₂. Wearing resistance of the coatings was greatly improved and corrosion resistance of Ni60 cladding is better than that of the 45# steel. Experimental results shows that rare-earth oxide added laser cladding coating has distribution and dimension phases, corrosion resistance property of laser cladding coatings are also enhanced.