Functionally graded IN718-WC composites cladding on 17-4 ph martensitic stainless steel via laser powder bed fusion additive manufacturing

Inconel 718 (IN718) is widely used in cladding applications due to its excellent high-temperature strength, but its relatively low hardness and limited wear resistance reduce its functional performance. Incorporating tungsten carbide (WC) as a reinforcing phase can improve mechanical properties, though its high hardness and melting point present challenges for conventional cladding techniques. In this study, IN718-based composite clads reinforced with 20 wt.% WC were fabricated on a 17-4PH martensitic stainless steel substrate using Laser Powder Bed Fusion (L-PBF), and the effects of compositional grading on microstructure and mechanical performance were investigated. Three clad architectures were designed: a non-graded sample (NG-20), a graded sample with 5 wt.% WC increments (G-5), and a graded sample with 10 wt.% WC increments (G-10). Characterization included X-ray diffraction (XRD), optical and scanning electron microscopy (SEM), Vickers microhardness testing, and wear testing at room temperature and 350 °C using AISI 52100 steel pins. The primary phases identified were an austenitic γ-matrix, WC particles, and Laves phase, with in situ interfacial reactions forming diffusion layers around WC particles. Graded samples exhibited more uniform WC distribution and reduced porosity (<0.5%) compared to the non-graded sample (0.9%). All composite clads showed increased hardness, with NG-20, G-5, and G-10 increasing by 74%, 79%, and 91%, respectively. Wear tests revealed G-5 achieved the highest wear resistance, reducing wear rates by 38% and 42% at room temperature and 350 °C, respectively. G-10 reductions were 19% and 30%, and NG-20 reductions were 18% and 25%. Overall, the G-5 sample was identified as the optimal configuration, combining low porosity with enhanced mechanical performance.