Production and Characterization of Boride Coatings on Flame-Sprayed Martensitic Stainless Steel

Abstract

Thermal spray is a process with many industrial applications in surface protection against wear and corrosion. The benefits of these processes include increased component life and decreased equipment downtime. However, sometimes an even greater wear resistance is required for optimal results. In such cases, a secondary treatment may be performed to produce a duplex coating. The objective of this work is to evaluate the wear resistance of a borided flame-sprayed duplex coating using an AISI 410 martensitic stainless steel alloy and a flame-spray process. The boriding treatment was performed at 950°C with 2- and 4-h treatment time in liquid borax in which 10 wt. % of aluminum was added. Optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction, and Vickers micro-hardness were used to analyze the samples. Micro-adhesive wear tests were performed to evaluate the wear resistance of the coatings using the fixed-ball method. The duplex coating exhibited superior wear resistance and hardness. The flame-sprayed coating layer exhibited a base hardness of about 450 HV, which was increased four times to about 1950 HV by including the boriding treatment. The thickness of the borided layer was approximately 50 μm.