Abstract
Thermally-sprayed Fe-based coatings have shown their potential for use in wear applications due to their good tribological properties. In addition, these kinds of coatings have other advantages, e.g., cost efficiency and positive environmental aspects. In this study, the microstructural details and tribological performances of Fe-based coatings (Fe-Cr-Ni-B-C and Fe-Cr-Ni-B-Mo-C) manufactured by High Velocity Oxygen Fuel (HVOF) thermal spray process are evaluated. Traditional Ni-based (Ni-Cr-Fe-Si-B-C) and hard-metal (WC-CoCr) coatings were chosen as references. Microstructural investigation (field-emission scanning electron microscope FESEM and X-Ray diffractometry XRD) reveals a high density and low oxide content for HVOF Fe-based coatings. Particle melting and rapid solidification resulted in a metastable austenitic phase with precipitates of mixed carbides and borides of chromium and iron which lead to remarkably high nanohardness. Tribological performances were evaluated by means of the ball on-disk dry sliding wear test, the rubber-wheel dry particle abrasion test, and the cavitation erosion wear test. A higher wear resistance validates Fe-based coatings as a future alternative to the more expensive and less environmentally friendly Ni-based alloys.
Highlights
Wear is among the most serious of issues to deal with when contacting surfaces in machine parts are in relative motion, such as in bearings, joints, gears, shafts, hydraulic parts, mining industry machines, components in aeronautical industry and others
thermogravimetry analysis in air (TG) analysis performed in air revealed a noticeable gain of weight starting at about 1000 °C due to oxidation
This study focused on the microstructural and mechanical characterization and on the tribological behavior of novel High Velocity Oxygen Fuel (HVOF)-sprayed Fe-based coatings compared to conventional HVOF-sprayed
Summary
Wear is among the most serious of issues to deal with when contacting surfaces in machine parts are in relative motion, such as in bearings, joints, gears, shafts, hydraulic parts, mining industry machines, components in aeronautical industry and others. Great effort has been undertaken to minimise wear cost by design or material changes. In such a scenario, surface coating technology has gained growing interest in recent years. Among various surface coating techniques, thermal spraying has been recognized as one of the most feasible and cost-effective solutions to protect against wear and corrosion [2]. The High Velocity Oxygen Fuel (HVOF) spray process developed in the 1970s is well known as the standard technology for depositing high wear and corrosion resistant coatings. Fuel gas (propane, ethene, hydrogen) or liquid (kerosene) are mixed in a combustion chamber with oxygen at high pressure. The exhaust hot gases generated by the combustion are forced to pass through a convergent-divergent nozzle reaching supersonic velocity
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