Fabrication and properties of micro-additive manufactured Ni-based composite coatings by short-pulsed laser

Abstract

Laser micro-additive technology exhibits excellent promising applications in processing microelectronic components, fabricating medical implants and improving local properties of micro-devices. In this paper, laser micro-additive technology is utilized to fabricate Ni-based micro-cladding coatings by a short-pulsed laser with the pulse width of 10 ns and maximum power of 20 W, and the effect of laser process parameters on micro-cladding coatings is investigated. Results exhibit that the surface quality of micro-cladding coatings is seriously influenced by the process parameters, and the optimal laser process parameters: power of 16 W, scanning speed of 20 mm/s, transverse overlap ratio of 0.8 and frequency of 20 kHz (laser energy density of 160 J/mm3) are obtained. Subsequently, the immersion tests are carried out for evaluating the oxidation and corrosion properties of Ni-based coatings, and the coatings with the thickness of 10–15 μm exhibit excellent anti-oxidation and anti-corrosion properties compared to substrate due to the shielding effect of micro-cladding coatings. In oxidation region, Fe3O4 and Fe2O3 oxidation layers are formed on substrate accompanied by large amounts of β-FeOOH, γ-FeOOH and α-FeOOH; however, less oxidation reaction occurs on coating surface. In corrosion region, the substrate is covered by granular structures with more β-FeOOH, γ-FeOOH and a few α-FeOOH, and the coating surface is quite smooth with few defects of exfoliation.