Research On Laser Cladding In Situ Carbide Ceramic Reinforce The Iron Matrix Surface Composites

Laser cladding is an important surface modification technology, also known aslaser-plating or laser surface hardening. It is a surface modification method that using thecladding material to clad a layer on the substrate surface which based on high-energydensity laser-heat, so that to achieve metallurgical bonding with the substrate, andapproach a completely different composition and properties of alloy layer on the substratesurface compared with the substrate. The obtained alloy cladding which has a goodresistance to erosion, corrosion, wear resistance, as well as the performance that substratesthe lack of.In-situ process is developed in recent years as a preparation of new compositematerial technology, which is a chemical reaction under high temperature using moltenliquid metal and high reactivity of non-metallic vapor or solid phase, form a smalldispersion of ceramic reinforcement phase and forming a tight combination with the basemetals. In-situ reinforcements obtained in the reaction of the melt which has small size, theinterface clean and pollution-free, good thermal stability, as well as the well compatibilitywith the substrate and many other features.In the article, combine laser cladding and combustion synthesis, on the substrateof the45steel, the material of carbide ceramic reinforced iron matrix surface compositeswas prepared successfully. With adding rear earth elements and other measures to grainrefinement grain, with the method of controlling effective carbon content to improve thevolume fraction of reinforcement, the test parameters which can obtain a smooth claddinglayer have been got after many times experiments and mathematical model, use X-rayanalysis and other methods to reveal the mechanism of in-situ the carbide reinforcement.Cladding coating with carbide ceramic reinforcement and composites ceramicwere prepared by the laser clad in-situ technology, and the test parameters were improved. Resualts show that coating is mainly composed by the tungsten carbide and chromiumcarbide. The existence forming of W and C is WC, Fe₃W₃C and W₂C, and the existenceforming of Cr and C is mainly Cr₇C₃. The morphology of carbide is block, herringbone,including dendrites and so on by the SEM analyze. And optimize the preparing processparameters of laser in-situ carbide reinforcements and composites ceramic reinforcements.Study the fining behaver of the grains by adding rare earth oxides. There are a lotof network structures in the cladding layer, the networks are uniform and dense, SEM,XRD, EDS and AFM analysis show that the carbide ceramics reinforcement phases werecomposed of the network structure and network structures were the three-dimensionalstructure. After adding rare earth oxides organizations can be well refined and uniformed,the hardness of cladding layer was also improved.Analysis on the mechanical properties of the coating show that the coatingsmicro hardness increases prominently comparing with the substrate, which presentsgradient distribution with stable transition from the surface to substrate and is littleinfluenced by the coating composition for the good cladding quality specimen. The mainstrengthening mechanisms of the coating are fine grain strengthening, hardy particlesdispersing strengthening, super saturation solid solution strengthening and dislocationpile-up strengthening. The materials abrasive resistance increases prominently after lasercladding and the main abrasive mechanisms in the coating are Micro-grinding andMicro-tearing.The study will provide the guidance for the design, development and applicationof metal matrix surface composites.