Achieving superior hot corrosion resistance by PVD/HVOF duplex design.

• The introduction of Cr 3 C 2 -NiCr interlayer significantly extends the life of the CrN film at 550 °C. • The duplex coating exhibits superior high temperature oxidation resistance. • Top CrN film effectively improves hot corrosion resistance of Cr 3 C 2 -NiCr coating. • Chlorine-induced corrosion in uncovered holes is the main reason of top CrN film failure. In this study, an optimized duplex coating, consisting of a thick Cr 3 C 2 -NiCr interlayer and a top CrN film, were designed and deposited by HVOF and PVD. And then hot corrosion behaviors were systematically investigated, and corresponding corrosion mechanisms are discussed in detailed. Results showed that the thickness of the oxide scale of duplex coating is approximately one-tenth that of the Cr 3 C 2 -NiCr coating. Due to the formation of Cr 2 O 3 oxide film, the CrN/Cr 3 C 2 -NiCr duplex coating exhibits superior hot corrosion resistance. However, chlorine-induced corrosion in uncovered holes is the main cause of local failure of duplex coating. [ABSTRACT FROM AUTHOR]