Effect of Substrate Preheating on Cracking and Wear Resistance of Laser-Cladded Tribaloy T-800 Coatings on DD5 Single-Crystal Alloy

This study aims to investigate the impact of substrate preheating on the cracking and wear resistance of laser-clad T-800 alloy coatings on DD5 single-crystal alloy substrates. Two different conditions, namely non-preheated (22 °C) and preheated (300 °C), were employed to deposit T-800 alloy coatings on the surface of DD5 single-crystal alloy using laser cladding technology. The experimental results reveal that substrate preheating at 300 °C reduces the degree of variation in microstructure morphology within each region of the coating. This reduction effectively mitigates the internal stresses caused by the difference in solidification rates of the various parts of the coating, thereby preventing coating cracking. Additionally, the presence of Ni in the DD5 substrate enhances the dilution effect on the coating. Compared to the non-preheated condition, the preheated condition increases the Ni content in the primary Laves phase, secondary spherical Laves phase, and Co-based solid solution of the coating by 6.6%, 7.5%, and 14.8%, respectively, and the Co, Cr, Mo, and Si contents were all reduced. Consequently, this reduces the primary Laves phase and secondary spherical Laves phase precipitation and further inhibits coating cracking. The crack defects within the coating in the non-preheated condition of the substrate weakened its wear resistance. Despite a 13.6% reduction in coating microhardness attributed to preheating of the substrate, the high hardness properties of the T-800 alloy coating were preserved. Moreover, the internal hard Laves phase structure was more diffusely distributed in the softer Co-based solid solution, resulting in improved wear resistance through increased anti-adhesion ability and resistance to hard particles intrusion. Specifically, the preheated coating shows a 14.0% reduction in average coefficient of friction, a 37.9% reduction in mass loss. The wear mechanisms observed in the coatings include abrasive wear, adhesive wear, and oxidative wear.