Achieving High-Quality Formed Hastelloy X Cladding Layers on Heterological 50CrVA Surface by Optimizing Process Parameters in Directed Energy Deposition

Hastelloy X exhibits outstanding thermal fatigue resistance, making it a promising material for repairing 50CrVA landing gear via directed energy deposition (DED). However, the substantial differences in composition and thermophysical properties between 50CrVA and Hastelloy X pose challenges by affecting interfacial microstructure and surface quality. This study investigates the effect of DED process parameters (laser power <i>p</i>, powder feed rate <i>f</i>, scanning speed <i>v</i>, and overlap rate) on the dilution ratio (<i>η</i>), microscopic morphology, surface flatness (<i>ζ</i>), and porosity of Hastelloy X claddings on a 50CrVA substrate. An optimization methodology integrating thermal-flow coupled simulation models and orthogonal experiments is developed to fabricate high-quality claddings. Furthermore, the corrosion-wear performance of the claddings is evaluated. The results indicate that the <i>η</i> of a single track increases with higher <i>p</i> or lower <i>f</i>, while it first increases and then decreases with the increase in <i>v</i>. Ablation marks tend to occur at excessive <i>p</i> or insufficient <i>f</i>, while low <i>v</i> causes surface ripples. The <i>ζ</i> of a single layer initially improves and subsequently deteriorates with increasing overlap rate. Porosity is significantly influenced by <i>p</i> and <i>f</i>. The optimal <i>p</i>, <i>f</i>, <i>v</i>, and overlap rate are 1600 W, 2.4 g/min, 240 mm/min, and 55%, respectively. The wear resistance of the cladding is nearly identical to that of the substrate, while corrosion resistance is significantly improved. This work provides a theoretical foundation for high-performance repair of 50CrVA landing gear in aircraft.