Deposition of high-velocity oxygen-fuel (HVOF) coatings on laser-powder bed fused (L-PBF) parts subjected to in-situ laser remelting treatments

Abstract

In this work, we focused on enhancing the adhesion between High Velocity Oxygen-Fuel (HVOF) sprayed coatings and Laser-Powder Bed Fused (L-PBF) substrates by modifying the substrate surface through in-situ laser remelting treatments. Additionally, we investigated whether deposition on laser-treated substrates affected the coating microstructure and performance. Therefore, WC-10%Co-4%Cr coatings were deposited on AISI 316 L stainless steel substrates in as-built conditions and after two different in-situ laser remelting treatments. All substrates were coated both before and after a pickling treatment. Grit-blasted bulk stainless steel samples served as references.

Laser remelting changed the morphology of the L-PBF surfaces depending on the laser parameters used. The most energetic treatment resulted in more widely spaced grooves and melted the unmelted spherical particles attached to the as-built surface, leading to a more uniform material distribution. These changes influenced the adhesion-cohesion of the coatings. Although all tensile test failures were primarily cohesive, the coatings deposited on the substrates subjected to the most energetic treatment exhibited an increased adhesion-cohesion strength, exceeding 80 MPa, while all other samples showed values around 70 MPa.

When the substrate was subjected to remelting treatments, however, the corrosion resistance of the coated systems decreased due to faster substrate corrosion in areas exposed to corrosive agents penetrating through coating defects.