Boriding of HVOF-sprayed Inconel 625 coatings

• Published in: Surface & coatings technology 2020-12, Vol.404, p.126456, Article 126456
• Main Authors: Lindner, Thomas, Löbel, Martin, Hunger, Ralph, Berger, Robin, Lampke, Thomas
• Format: Article
• Language: English
• Subjects: Boriding; HVOF; Inconel; Precipitation hardening; Thermochemical treatment; Wear
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2020.126456

The efficient application of high-performance materials under harsh environmental conditions requires advanced coating technologies and the combination of different surface processes. Thermal spraying of metallic coatings with a subsequent diffusion treatment results in a unique combination of bulk and surface properties. A hardening of high-velocity-oxygen-fuel-sprayed Inconel 625 coating systems is performed by powder-pack boriding. In addition to the as sprayed condition, the thermochemical treatment was carried out on solution annealed coatings. Delamination did not occur during the post-treatment due to the good coating adhesion. The microstructure evolution and phase formation are analysed in detail. The successful diffusion of boron within a homogeneous precipitation layer is proven. A distinct increase in microhardness and wear resistance could be achieved. The significant improvement in tribological performance was achieved independently of the pre-treatment state. The correlation between structural and mechanical properties contributes to a better understanding of the material behaviour. In the context of current efforts to improve wear resistance, the presented results provide a new approach comprised of a two-step surface engineering process. •Process combination of thermal spraying and thermochemical treatment•Powder pack boriding of IN625 HVOF coatings•Formation of the homogeneous precipitation layer•Strong increase in microhardness and wear resistance