Characterization and tribological properties of boride coatings of steels in a fluidized bed reactor

Abstract

Purpose - The aim of the current research is to characterize boride coatings on steels and steel alloys produced in a CVD fluidized bed reactor. Design/methodology/approach - Heat treatments of alloys in fluidized bed reactors have been carried out for more than 25 years. Recently, this technology has been used for surface engineering applications in the deposition of hard and/or corrosion-resistant layers. The present paper used fluidized bed technology (FBT) to deposit boride coatings on to ferrous materials. The coatings were examined by means of optical microscopy Vickers microhardness measurements and X-ray diffraction in terms of coating thickness and morphology, phase formation and hardness determination. The coating's tribological properties were evaluated under dry wear. Impact tests were also carried out to determine the fatigue resistance of the examined coatings under dynamic impact loading. Findings - Boriding in a fluidized bed reactor is a simple, environmentally friendly and fast-coating process. The produced iron-boride coatings are characterized by excellent quality and uniform tooth-shaped morphology. Fe2B was the predominant boride phase formed, exhibiting superior tribological properties under dry wear conditions. Impact testing investigations revealed high-fatigue strength of boride coatings in combination with limited deformable substrates. Research limitations/implications - The investigated coatings were deposited only on some structural and tool steel substrates. Practical implications - Boride coatings deposited using FBT are satisfactory abrasive wear- and fatigue-resistant coatings in comparison with those produced using common boride coating methods. Originality/value - The outcome of the research is of great importance for the industry using abrasive wear coatings.