Abstract
Cr3C2-25NiCr coatings were deposited on stainless steel substrates by high velocity air-fuel (HVAF) spraying. Friction and wear behaviors of as-sprayed and annealed coatings were investigated both at room-temperature (RT) and 600 °C (high-temperature, HT). The results show that annealing at 600 °C in air is effective to enhance the wear performances of the coating both at RT and HT. The enhanced wear resistance of annealed coatings is discussed from the oxide growth and the microstructural evolution of the coatings. The wear behavior of the annealed coating follows the abrasive mechanism at RT and changes to an oxidative wear at HT, in which formation of a tribo-oxide layer plays a critical role to reduce the friction coefficient and to protect the underlying coatings from abrasive damage. The findings of this work reveal the significance of oxide-scale growth and microstructural evolution on the HT wear behaviors of the Cr3C2-25NiCr coating, which provides strategies for enhancing the wear properties of such coatings for HT applications.
Highlights
Cr3 C2 -NiCr coatings are widely used in industrial equipment such as aircrafts, heat exchanger components and power recovery turbine [1] due to their excellent performance for oxidation, corrosion and wear protections [2,3,4,5,6]
Previous studies show that during high temperature exposure, Cr3 C2 -NiCr coatings are subjected to a variety of compositional and microstructural evolution including precipitation of carbides, equilibrium of Ni(Cr) saturated solid solutions and formation of oxide layers [1,7], which will have a large impact on the mechanical properties and the wear behavior of the coatings [13,14,15,16]
The as-sprayed coating mainly consists of crystalline Cr3 C2 and supersaturated supersaturated Ni(C,Cr) solid solution
Summary
Cr3 C2 -NiCr coatings are widely used in industrial equipment such as aircrafts, heat exchanger components and power recovery turbine [1] due to their excellent performance for oxidation, corrosion and wear protections [2,3,4,5,6]. Combining the high wear resistance from Cr3 C2 and the excellent oxidation and corrosion resistance from the binder phase (NiCr), Cr3 C2 -NiCr coatings can provide erosive [7,8] sliding wear [9] and abrasive [6,10] protections under a wide range of operating temperatures (i.e., >500 ◦ C) and even in aggressive environments [5,11,12]. Due to their high-temperature applications, it has raised increasing interests to improve the tribological properties at elevated temperatures of Cr3 C2 -NiCr coatings. Guilemany et al [14] carried out high-temperature heat treatment at 450–880 ◦ C in air and in argon, and investigated the effect of Coatings 2020, 10, 1090; doi:10.3390/coatings10111090 www.mdpi.com/journal/coatings
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