Effect of Ni-graphite content on microstructure and tribological properties of self-lubricating wear-resistant cladding layer on TC4 titanium alloy surface

Abstract

TC4/Ni60/Ni-graphite composite functional coatings with 25%(mass fraction), 35% and 45%Ni-graphite were prepared on TC4 titanium alloy surface by coaxial powder-feeding laser cladding technology. The forming quality, microstructure and mechanical properties of the composite coatings were studied by means of penetrant inspection, X-ray diffractometer, scanning electron microscope, energy spectrum analyzer, electron probe microanalyzer, white light interferometer, microhardness tester and friction and wear tester. The results show that the 35%Ni-graphite coating has the best forming quality, and different content Ni-graphite coatings have the same types of reaction precipitates, mainly Ti2Ni, TiC, TiB2, graphite and matrix α-Ti.The TiC coated graphite semi coherent composite phase and TiC, Ti2Ni cross growth coherent composite phase are formed in all coatings, the semi-coherent TiC coating can alleviate the melting of graphite in the molten pool, and the coherent TiC-Ti2Ni composite phase can make the brittle Ti2Ni structure uniformly refined. With the increase of Ni-graphite content, the average microhardness and wear resistance of the coatings decrease gradually, while the anti-friction performance first increases and then decreases, and the wear mechanism is abrasive wear.

Keywords

• laser cladding
• tc4
• ni-graphite
• composite phase
• tribology