Effects of Ta on the strengthening mechanism of microstructure and corrosion resistance of underwater wet laser cladding 17-4PH coating

Underwater wet laser cladding has gradually become the key technology for online repair of marine engineering materials. This work successfully prepared a Ta-reinforced 17-4PH coating on a 20Cr substrate using this technique. The study primarily examined how varying levels of tantalum (Ta) influence the microstructure, phase composition, microhardness, immersion corrosion, and electrochemical properties of underwater cladding coatings. Additionally, a detailed analysis of the corrosion mechanism was conducted. The experimental findings demonstrated that incorporating Ta can greatly enhance the forming quality and overall performance of coatings. When the Ta addition was 10 %, the forming quality was the best, and there were no porosity or depressions. The 10 % Ta coating had the best densification with a minimum porosity of 0.05 %. The average microhardness of the T10 coating was 594.1 ± 5.9 HV_0.2, an increase of about 13 % over the original T0 coating. Additionally, when the Ta content reached 10 %, the formation of Ta₂O₅ on the surface played a crucial role in enhancing the coating's resistance to immersion corrosion. The T10 coating demonstrates the highest polarization resistance and superior corrosion resistance among the coatings tested. The corrosion mechanism of the original unadded Ta coating involved severe intergranular corrosion and pitting; The corrosion mechanism observed in the T10 coating involved local crevice corrosion and minor pitting. This study reveals the strengthening mechanism of Ta on the organizational properties of the underwater laser cladding layer, which can provide meaningful guidance for the future development of underwater laser cladding technology.