Microstructure, performance, strengthening and toughening mechanisms of WC-reinforced Inconel 625 gradient composite coating by laser cladding on nonmagnetic steel

• Published in: Surface & coatings technology 2025-01, Vol.496, p.131657, Article 131657
• Main Authors: Zhang, Kai, Liu, Chenghui, Wang, Wenlong, Ju, Huaicheng, Liu, Weijun, Wang, Huiru, Bian, Hongyou
• Format: Article
• Language: English
• Subjects: Gradient composite coating; Inconel 625 alloy; Laser cladding; Microstructure and performance; Strengthening and toughening mechanism; WC particle reinforcement
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2024.131657

To enhance the surface properties of nonmagnetic steel, WC-reinforced Inconel 625 gradient composite coating was fabricated using laser cladding. The coating exhibited a layered structure with increasing WC content from the bottom layer to the top layer, promoting a gradual microstructural transition. The hardness of gradient composite coating increased progressively from 447.48 HV1 in the first layer to 529.88 HV1 in the third layer. The hardness of the third gradient layer was 1.78 times that of the substrate and 1.15 times that of the 30 % WC uniform composite coating. Moreover, the gradient coating exhibited the lowest wear loss, amounting to 0.6 mg, with a wear rate of 0.42 × 10−3 mg·m−1·N−1. The wear resistance of the gradient coating was enhanced by 94 %, 85 %, and 57 % in comparison to the substrate, Inconel 625 coating, and 30 % WC coating respectively. The gradient coating also demonstrated improved corrosion resistance, with the corrosion rate of 0.67 g/(m2·h) after salt spray corrosion, and the polarization resistance of 13,550 Ω·cm2 in 3.5 wt% NaCl solution. In addition, the gradient structure effectively reduced residual stresses, aligning with the thermal expansion properties of the substrate and minimizing stress concentration. Accordingly, the experimental results prove that the strengthening and toughening mechanisms of the composite constituents, the uniform transition of composition and microstructure, and the coupling effects of the bonding interface collaboratively lead to the improvement and enhancement of the comprehensive performance of the gradient composite coating. This study provides a promising solution for enhancing the surface properties of nonmagnetic steel for applications in harsh environments. •Gradient composite coating achieves synergistic strengthening and toughening effects.•Gradient composite coating shows gradual transition in WC content and microstructure.•Gradient composite coating shows superior hardness, wear and corrosion resistance.•Gradient composite coating can better accommodate the thermal expansion mismatch.•Gradient composite coating reduces residual stress and relieves stress concentration.