Tribological behaviors of CrN/Cr3C2-NiCr duplex coating at elevated temperatures.

Duplex coating, composing of a thick Cr 3 C 2 -NiCr interlayer and a top CrN film, were deposited by high velocity oxy-fuel (HVOF) and arc ion plating technologies, and the microstructure, mechanical properties and thermal shock resistance of the duplex coating were investigated compared to those of the single CrN film, as well as tribological behaviors at elevated temperatures. Results showed that the duplex coating exhibited high surface hardness, H / E and H 3/ E 2 ratios, load-bearing capacity and adhesive strength due to the supporting of the Cr 3 C 2 -NiCr interlayer, which contributed to improve the wear properties of duplex coating sliding against Al 2 O 3 ball. At 25 °C, the duplex coating had a higher friction coefficient and a relatively low wear loss, and the main wear mechanism was abrasive wear. As the temperature increased to 350 °C, the top CrN film of duplex coating was worn out totally. The severe mismatch of coefficient of thermal expansion (CTE) between Cr 3 C 2 -NiCr interlayer and substrate that might have a negative impact on wear resistance of duplex coating at high temperature. In addition, a large number of debris produced due to oxidation peeling of the coatings were compacted to form a thick transfer film during the sliding process, resulting in badly adhesive wear. The wear mechanisms were adhesive and oxidation wear accompanied with abrasive wear at high temperature (from 150 °C to 550 °C). • The CrN/Cr 3 C 2 -NiCr duplex coatings are fabricated by PVD/HVOF. • Duplex coatings show superior mechanical properties than single PVD film. • Cr 3 C 2 -NiCr interlayer significantly improves wear resistance of CrN film at 25 °C. • Mismatch of CTE in duplex coating and friction induced oxidation results in severe wear above 150 °C. [ABSTRACT FROM AUTHOR]