| By using laser cladding technique and preplacing different alloy powders mixture of NiSiTi+WC, NiSiTi+(Ti+C) on Nickel-based superalloy substrate as well as C, TiC, (Ti+C), (Ti+TiC), (Ti+WC+C) on commercial pure titanium TA2 substrate, a series of ceramic reinforced metal matrix and intermetallic compound matrix composite coatings which obtained excellent metallurgical bonding with substrate were fabricated. Microstructure of clad layers was characterized with research methods of XRD, SEM, EDAX, and EMPA. Microhardness of clad layers was measured through HVS-1000 type microhardness tester. And the in-situ reaction during the process was analyzed.Phases of laser cladding intermetallic compound matrix composite coatings through preplacing Ni78Si13Ti9+WC on Nickle-based superalloy substrate are composed of Ni solid solution, Ni3(Si,Ti) intermetallic compound and (Ti,W)C carbide. And phases of laser cladding Ni78Sil3Ti9+(Ti+C) composite coatings are composed of Ni solid solution, Ni3(Si,Ti) intermetallic compound and TiC. The microhardness distribution curve of clad layers is composed of three parts: clad layer of the tallest value, heat-affected zone of medium value and substrate of the lowest value. The microhardness of the clad layer with 20wt% (Ti+C) content attains to Hv780, which is 2.5 times of the substrate. This is because of the formation of rapidly solidified fine microstructure of TiC reinforcement.The results show that phase of coatings by preplacing C, TiC, (Ti+C) and (Ti+TiC) powders respectively on TA2 substrate are all composed of α'-Ti and TiC. Phases of laser cladding (Ti+C+WC) coating are composed of α'-Ti, W, TiC and (Ti, W)C. During laser processing of the coatings containg WC produced on TA2 and GH864 substrate, in-situ TiC forms when the partially melting WC particles react with liquid Ti and then TiC transforms to (Ti,W)C solid solution type carbide. The formation course of multiple carbide (Ti,W)C is explained by establishing a simple model. |
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