In-situ Synthesized Ti-B-C Superhard Were-resisting Composite Coating Of TC4Titanium Alloy By Laser Cladding Combined With Laser Remelting

Laser surface strengthening of the typical TC4titanium alloy parts is researchedin this paper. Using micro-hardness tester, Scanning Electron Microscopy (SEM),Optical Microscope (OM) and X-Ray Diffraction (XRD) to analyze the organizationand performance of the in-situ synthesis ceramics coating. The rules of organizationforming and micro-hardness fluctuation were mainly analyzed，then the strengtheningmechanism of cladding was studied. the results showed as follows:(1) Summarize and analyze the current of the in-situ formation of the typicalTC4titanium alloy by laser cladding. Nowadays, It is using the high density energy oflaser beam to melting the cladding material, which is added on the surface of substrate,and metallurgical bonded with the substrate. Though, the bond strength betweencoating and body was low. The reaction between cladding material and the substratewas underutilized. It did almost nothing to control the industry costs.(2) when optimized laser parameters, the distribution of ceramic phase,morphology and microstructure of the cladding, which formed by melting TiB2power,were systematically researched. The result showed: the coatings had goodmetallurgical bond to the substrate, both crack and air hole are not found. Themicrostructures changes first appeared massive, then fine acicular from the surface ofthe layer to the substrate in the depth direction. At the same time, percent of the TiB2ceramic reinforcement phases was lower and lower, the TiB one’s was higher andhigher. The variation of layer’s micro-hardness was vary gradually from the substrateto the surface of the layer in the depth direction. It was composite modification, andthe microstructure of cladding mainly showed fibrous and particle shape. (3) Preset a certain thickness of B4C coating on the titanium alloy surface, in-situformation to get composite cladding by laser irradiating, and clad the in-situ coating.Then, the microstructure, phase distribution and micro-hardness of the coating werecompared with the out-clad coating’s. The results showed: the optimized processparameters of in-situ formation laser cladding could be good at decreasing air hole atthe bottom and making ceramic phase well-distribute to fine the microstructure ofcoating. After the laser cladding, the gradient of layer’s micro-hardness was smoothly,the average micro-hardness was higher and the whole quality of layer was improved.