Hardfacing of Fe-Cr-C alloy on carbon steels

Hardfacing is a surface engineering technology used to deposit a protective layer on the surface of a base material, aiming to enhance its surface properties or repair damaged areas. It is commonly used to protect and maintain critical components such as valves, pipelines, pressure vessels, turbine blades, and mining equipment from harsh operating conditions, thereby extending service life and reducing maintenance costs. As a result, hardfacing technology is widely applied across industries, including oil and gas, petrochemicals, power generation, mining, and aerospace. However, research on the application of hardfacing to strengthen and repair AISI 1045 steel and quenched-tempered (Q&T) steel remains limited, particularly in the case of Q&T steels.This study employs austenitic stainless steel (ASS) as the interlayer and an Fe-Cr-C alloy as the overlay in multi-layer welding on AISI 1045 steel and Q&T steels, including RHA (Rolled Homogeneous Armour), UHT (Ultra High Toughness), and HHA (High Hardness Armour). The approach aims to explore a potential solution for enhancing the surface strength of AISI 1045, RHA, and UHT steels, as well as for repairing HHA, permitting a systematic investigation of process-microstructure-property interrelationships in hardfacing technique on the researched materials via simulation and experiments.Multilayer welding experiments incorporating an ASS steel interlayer and an Fe-Cr-C alloy overlay were conducted on AISI 1045 steel first, accompanied by numerical simulations of the welding process. The microstructural characteristics at different interfacial regions after welding were examined experimentally and validated against simulation results, to elucidate the influence of the welding process on microstructural evolution. Furthermore, the numerical simulations focused on the distribution and evolution of temperature and stress fields, while also accounting for dynamic phase transformations during welding. These simulations contribute to a deeper understanding of post-welding thermal evolution, phase transformation behaviour, and the development of residual stresses.Subsequent wear and corrosion tests were conducted on the multilayer welding structure deposited on AISI 1045 steel to evaluate the performance of the three-layer system. The results indicate that this three-layer hardfacing structure significantly enhances the wear resistance and corrosion resistance of the steel substrate.Given the multilayer welding results obtained on AISI 1045 steel, this study further extends the investigation to Q&T steels, incorporating heat treatment and arc oscillation techniques. The research specifically focuses on how arc oscillation influences the interfacial microstructural evolution and performance of multilayer welding structures in Q&T steels. A refined microstructure and enhanced mechanical properties were achieved through the optimisation processes.Based on the outcomes achieved in this work, it can be found that, in the Fe-Cr-C/ASS/AISI 1045 multilayer hardfacing structure, different interfacial regions exhibited distinct microstructural characteristics, with the Fe-Cr-C layer and the AISI 1045 steel layer showing higher levels of deformation and residual stress.Finite element simulations demonstrated good agreement with the experimental results, indicating the dynamic evolution of the temperature field, solid-state phase transformations, and stress field during the hardfacing process. The multilayer hardfacing structure enhanced the wear resistance and corrosion resistance of the substrate. Arc oscillation was found to facilitate microstructural refinement in the multilayer hardfacing structure, mitigate the interlayer hardness gradient, and thereby enhance the performance of the hardfacing layers.