Preparation Of Ni-coated Cr₃C₂ Powder By Electroless Plating And Its Application To Laser Cladding

Comparing with metal, ceramic materials have their own advantages, such as higher melting point, higher strength, better wear resistance and anti-corrosive properties. however, their brittleness and hard to process restrict their application. Material surface engineering is to change surface morphology, chemical constituents, microstructure and stress state of metallic or nonmetallic solids, via surface coating, surface modification and composite technology, to obtain good comprehensive performance. In this study, ceramic powder, coated with nickel alloy by electroless plating, were used as laser cladding material. After cladding process, the sample combined the advantages of both steel substrate and ceramic coating properties.In this paper, ductile nickel was deposited on the surface of micron Cr₃C₂ ceramic particles to obtain Cr₃C₂-Ni synthetic powder via low temperature electroless plating process with supersonic enhancement. This nickel layer on the Cr₃C₂ powder formed as dense and uniform cell structure. The pretreatment process was simplified greatly from coarsening, sensitizing and activating as common procession to coarsening only, that is environmental friendly and energy saving.Without inducing extra alloy powder as bonding ingredient, the synthesized Cr₃C₂ powder were used as laser cladding material to obtain Cr₃C₂-Ni layer on steel substrate. Also, wet ability of ceramic powder with metal was improved considerably with nickel on the Cr₃C₂ powder as interlayer.While laser power was 2.0 kW with scanning velocity at 500 mm·min^-1 and 4 mm spot diameter, the microstructure of the cladding coating was fine and unifor. The layer bound with substrate tightly to form alloy transition zone with a continuous and clear interface. Because of the interaction between unmelted Cr₃C₂ powder and ductile metal, the average hardness of cladding layer was HV_0.11073.5, which was approximately 5 times of the substrates hardness. The Cr₃C₂-Ni laser coatings performed stable friction state and friction coefficient kept at about 0.4. At the same time, it had appeared good wear resistance.