Arc deposition oxide-modified H13 steel: Investigating the structure of oxygen-containing second-phase particles and their influence on the microstructure

The challenge associated with depositing high-strength steel using the arc deposition method lies in the propensity for hardened microstructures to form during the deposition process. This hardened microstructure can lead to a decrease in material toughness and potentially cause cold cracks. Fortunately, oxide metallurgy technology is expected to address this issue. Specifically, nano oxides can refine the grain and induce the formation of intracrystalline ferrite, thereby enhancing steel's toughness. To gain a deeper understanding of this process, a study was conducted on the morphology and structure of oxygen-containing second-phase particles generated in parts made from H13 steel wire modified with Al2O3, TiO2, and SiO2. Additionally, the impact of these oxygen-containing second-phase particles on microstructure transformation was investigated. The following conclusions were drawn from the study: (1) The arc's high temperature causes complex reactions among the oxides in the molten pool, ultimately resulting in the formation of oxygen-containing second-phase particles with a unique core-shell structure. The size and composition of these particles vary within the interdendritic and intradendritic regions due to element segregation. (2) Through in-situ observations, this study discovered that oxygen-containing second-phase particles promote the nucleation of high-temperature ferrite and austenite. This promotes grain refinement and induces the formation of intracrystalline ferrite, which positively impacts material toughness. (3) The driving force for ferrite phase transformation induced by oxygen-containing second-phase particles may stem from the Mn-depleted zone surrounding the particles and the low mismatch between the VC outer layer of the particles and the ferrite.