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Formation mechanism and microstructural and mechanical properties of in-situ Ti-Ni-based composite coatings by laser metal deposition

: Ma, C.; Gu, D.; Hong, C.; He, B.; Chang, K.; Shi, Q.


Surface and coatings technology 291 (2016), pp.43-53
ISSN: 0257-8972
Journal Article
Fraunhofer ILT ()

The in-situ TiO2 reinforced Ti-Ni composite coating on carbon steel was successfully prepared by laser metal deposition (LMD) using Ti-Ni as-mixed powder with an atomic ratio of 60:40. With the aim of in-situ reaction design during LMD processing, a trace of oxygen mixed with the shielding gas was introduced. Different "laser energy input per unit length" (E) by changing the laser power was set to investigate the influence on the deposition quality and attendant microstructure and mechanical property of the LMD-processed layer. TiO2 particles with unique flower-like structure formed when the applied laser energy E <= 96 kJ/m, while the apparent oxidation of grain boundaries was observed as E increased to 120 kJ/m. The formation mechanism of in-situ TiO2 particles with a flower-like structure was present. At the optimized process parameter of 96 kJ/m, the LMD-processed layer showed the highest densification degree free of any pores and cracks. The corresponding mechanical properties were measured, showing the relatively high average microhardness of HV0.2 790 and significantly improved tribological property containing lower coefficient of friction of 0.4 and more smooth worn surface.