Detonation Spraying of a Cermet Coating to Improve the Surface Properties of Tool Steel Parts Produced by the Selective Laser Melting Process

Abstract

In this study, a novel attempt was made to deposit 86WC-10Co-4Cr cermet layer on 1.2709 tool steel substrate prepared by selective laser melting (SLM) process using detonation spraying method. The laser power of 350 W, scan speed of 25 mm/s, hatch spacing of 0.15 mm, and layer thickness of 50 µm were used to fabricate samples at 45° build orientation. The calculated volumetric energy density for fabricating the samples was 1867 J/mm³. The SLM printed samples were annealed and air cooled at 500 °C in a box furnace with a dwell time of 6 h. The average particle size of the powder measured before and after the ball milling process was 237.49 and 43.06 μm, respectively. A coating thickness of 100 μm was targeted using the detonation spraying process. An average spray loss of 13% was observed during cermet coating. The results were compared between the as-built specimen, the heat treated specimen and the 86WC-10Co-4Cr coated specimen. The average Vickers microhardness of the coated sample was found to be 81.04 and 48.96% superior to the as-built and heat treated samples. The average contact angles measured from the as-built, heat treated and coated samples were 82.5°, 64° and 93.9°, respectively, indicating the superior hydrophobic surface in the coated sample. The coated sample offered reduced abrasive wear, improved corrosion inhibition, and better 2D and 3D surface roughness properties than the as-built and heat treated samples, which promises its further use in cermet-based rapid tooling applications.