Investigation on microstructure and corrosion resistance of inconel 625 overlay coating on 35NiCrMoV123 ultra-high-strength carbon steel

The ultra high strength steel, DIN 1.6959 (35NiCrMoV123) has application manufacturing military components such as gun harrels. The service conditions for these components are hige pressure, hot corrosion and oxidation, which leads to incremd in inner radius of the gun harrels and for mation of fine cracks on inner surface, which resulte in failure. Weld overlay by arc welding processes are appropriate process for repair of these components In this research, Gas-tungsten arc welding (GTAW) process and pre-heat temperature of 2000C on mentioned steel, a Inconel 625super alloy weld overlay was developed. Later, microstructure of different welde zones and it إs corrosion resistance was measured by corrosion polarization test. Results indicate that by pulse welding the fusion area’s thickness would decrease by 40% and hardness of the base metal beside the welded metal was reported between 56 to 47 rockwell C and welded metal was 22 to 20 rockwell C. The reduction in corrosion vate in overlay specimens is significant compared to the base metal. The potential of overlay samples is higher than the base sample. The base metal structure was tempered martensitic, the microstructure is uniform and no course martensitic blades are observed in the structure. Also, Inconel 625 superalloy to a depth of 120 to 140 μm has penetrated into the base metal.

Keywords:

DIN 1.6959 (35NiCrMoV123) ultra-high-strength low carbon steel , Inconel625 , TIG process , microstructure , corrosion resistance