Investigation Of In-situ Synthesized Boride And Nitrides Reinforced Fe Matrix Wear-resistant Coating By TIG Arc/Cored-wires Weld Overlaying

As the tube welding wire cladding alloy powder, cored-wire has been expanded by leaps and bonds to be used as a kind of high efficiency and high quality of surfacing materialsin recent years. Composite coatings by TIG/cored-wire weld will avoid the introduction of impurity phase in interface and surface to keep clean. And the small weld heat input can maximum limit retains effective components from the molten cored-wire within the surfacing layer. At the same time, less impurities pollution in the interface between the second phase by in-situ synthesized and the matrix phasecan significantly improve the combination of the two phase interface.The in-situ synthesis not only can achieve anexpectable microstructure of the second phase in the materials, but also with the special performance.The joint application of the TIG/cored-wire weld and the in-situ synthesized technology has not been reported up to now.TiB2 and TiC particulates reinforcing Fe matrix composite coatings were in-situ synthesized on the surface of Q235 steel by TIG arc melting cored-wires containing Cr、Ni、FeTi、Ti、B4C and FeB powders. The microstructure, micro-hardness and wear resistance of the weld overlay coating were investigated using SEM, XRD, Micro-hardness Tester and Pindisc Wear Tester respectively. And the formation mechanism of TiC and TiB2 particulate was discussed.TiCNparticulates reinforcing Fe matrix composite coatings were in-situ synthesized on the surface of Q235 steel by(Ar-N2) TIG arc/cored-wire weld. The microstructure, micro-hardness and wear resistance of the weld overlay coating were investigated using SEM, XRD, Microhardness Tester and Pin-disc Wear Tester respectively. And the formation mechanism of TiCN particulate was discussed.The results showed that the weld overlay coating presented a dense microstructure with defect-free of pore and crack, and better metallurgical bond with the substrate; TiC and TiB2 distributed dispersively in Fe matrix of the weld overlay coatings, where TiC particle appeared in the form of dendrite flower-like and cubic morphology and TiB2 in the form of clubbed and hexagonal shape. The high Micro-hardness of the coating was 1657.58 HV. The coating from cored-wire designed 55 wt. % content of TiB2 obtained the best wear resistance. The TiC and TiB2 particle formation mechanism of nucleation and growth via liquid diffusion and liquid-solid diffusion was proposed. TiCN/ Fe matrix composite coatings were in-situ synthesized in the surface of Q235 steel substrate by(Ar-N2) TIG arc/cored-wire weld overlaying process. The results showed that when the nitrogen content in Ar-N2 mixing arc changed between 25% to35%, the weld overlaying coatings had a good quality without pores or cracks, but up to 40%,pores and cracks would occur in the weld overlay coating, and the TiCN particulates with size range of 1-3μmwere dispersively and uniformly distributed in the Fe-matrix of the weld overlay coatings. Furthermore, the coating micro-hardness was a range of 1385 HV to1736.40 HV, leading to the wear resistance significantly increasing.