The Effects of HVOF Coating of WC-CrC-Ni Powder on In718 and of CO2 Laser Heat Treatment on the Coating

다국어 초록 (Multilingual Abstract)

High-velocity oxygen-fuel (HVOF) thermal-spray coating (coating) of micron-sized WC-CrC-Ni
was carried out on an Inconel718 (In718) surface to improve the surface properties, friction and wear
behaviors. During the spraying, binder metals were melted and a small portion of metal carbides,
such as WC, Cr7C3 and Ni3C, were melted, partially melted, or decomposed to W2C, Cr, Ni and
free carbon. A porous coating was formed by the evolution of carbon oxide gases formed by the
reaction of the free carbon and the sprayed oxygen gas. For further improvement, a CO2 laser heat
treatment (LH) was performed on the coating. Laser beam (10.6 μm, continuous mode, 400 W)
irradiated an oval-shaped focal spot (5 mm × 4 mm) for 0.6 s at a scanning speed 400 mm/min,
heating to about 950 - 1200℃ from the edge to the center of the spot. Laser tracks overlap each
other 30 %. The porous coating was compacted by the LH, reducing the coating thickness by about
29 % from 280 μm to 200μm and the porosity by about 7 times from 2.6 ± 0.4 % to 0.35±0.06
%. The surface hardness of In718 (410±30 Hv) was increased more than twice to 983±101 Hv
by the coating; furthermore, it was increased 45 % (1425±94 Hv) by LH for 0.6 s. The friction
coefficient of the In718 surface (0.45±0.08) was reduced 29 % (0.32±0.02) and 9 % (0.29±0.03)
by the coating and by the LH, respectively. The wear depth was reduced from 52μm to 30μm and
to 12μm by the coating and by the LH, respectively. A HVOF coating of WC-CrC-Ni powder on a
metal surface and a LH of the coating are highly recommended for improving the surface properties,
the friction behavior and wear resistance.

참고문헌 (Reference)

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