Abstract
In the present work, we investigated the microstructures and properties of as-sprayed and annealed CoMoCrSi coatings. Specifically, the annealed treatment at 800 °C resulted in good recrystallization, improved microstructure, and enhanced properties of CoMoCrSi coatings. An oxide layer formed on the annealed coating surfaces; it was mainly composed of nano-sized Cr2O3 and micro-sized CoMoO4, and could account for the increased surface microhardness and enhanced anti-wear performance of annealed coatings. In particular, the very hard Cr2O3 played a critical role of resisting press-in and wear during the tests, and the CoMoO4 had a lubricating effect during the friction process. Finally, the annealed coatings exhibited low coefficients of friction (COFs) of 0.4 and wear rates of 0.7–0.8 × 10−6 mm3·N−1·m−1 after a long sliding distance of 1000 m at RT. Consequently, the wear mechanism transferred from brittle fracture coupled with abrasive wear for the as-sprayed coating to slight abrasive wear for annealed coatings.
Highlights
A report [25] indicated that annealing treatment at 600 and 1000 ◦ C could lead to the phase transformation, and improvement in mechanical and tribological properties of the atmospheric plasma spraying (APS)-sprayed CoMoCrSi coating
We have evaluated the tribological properties of the high-velocity oxygen fuel (HVOF)-sprayed CoMoCrSi coatings in a wide temperature range [18]
We investigated the following: (a) the microstructure and phase transformation of CoMoCrSi coatings before and after annealed treatment, (b) the influence of oxide formation on the mechanical and tribological properties of CoMoCrSi coatings at room temperature (RT), and (c) the wear mechanisms of CoMoCrSi coatings
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Sprayed coatings have been widely applied to provide necessary protection against oxidation, wear, and corrosion in various industrial fields, e.g., the traditional machinery industries (gears, rollers, valves, bearings, wheels, axles, and drills), ocean engineering, and aerospace industries [1,2,3,4,5,6,7,8,9,10] They are a low-cost, effective way to enhance the surface properties and to prolong the service life of related mechanical parts. A report [25] indicated that annealing treatment at 600 and 1000 ◦ C could lead to the phase transformation, and improvement in mechanical and tribological properties of the APS-sprayed CoMoCrSi coating. We investigated the following: (a) the microstructure and phase transformation of CoMoCrSi coatings before and after annealed treatment, (b) the influence of oxide formation on the mechanical and tribological properties of CoMoCrSi coatings at RT, and (c) the wear mechanisms of CoMoCrSi coatings
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