The Influence of the Second-phase Particles on the Oxidation Resistance of High-Mn Nickel-saving Austenitic Heat-resistant Steel and Its Mechanism of Oxidation

　　High-Mn nickel-saving austenitic heat-resistant steel with excellent mechanical properties and low Ni content is an ideal substitute for Cr-Ni austenitic heat-resistant steel. However, how to effectively solve the oxidation deterioration of austenitic heat-resistant steels caused by high manganese content is an important research topic and a difficult point to break through the limitations of its high-temperature application.

　　Based on previous researches from the research team of Professor Zheng Kaihong, an M2B+TiCN particle-reinforced Fe-18Cr-10Mn-4Ni steel has been prepared by the in-situ synthetic technology. The oxidation resistance of this steel has achieved a significant improvement. The problem of the poor anti-oxidation property of high-Mn austenitic heat-resistant steel at high-temperature has been solved. The oxidation mechanism of this new steel has also been revealed.

　　The results show that the introduction of the second-phase particles accelerates the outward diffusion of Mn to form a ferrite layer containing enough Cr to maintain the formation and growth of the Cr2O3 protective layer, thereby improving the oxidation resistance of high-Mn austenitic heat-resistant steel. The internal oxides generated by the selective oxidation of the second-phase particles has a pinning effect on the oxide layer to enhance the adhesion of the oxide layer (in Fig. 4). This study achieved a huge promotion in the oxidation property of high-Mn nickel-saving austenitic heat-resistant steel, simultaneously, provided a new idea for the alloy design of high-Mn austenitic heat-resistant steel.

　　This research was published in the international journal Corrosion Science in April 2021. Dr Tianlong Liu is the first author, and Professor Kaihong Zheng and Dr Zhichao Luo are the co-corresponding authors.

Fig. 1  The microstructure of (M2B+TiCN)p/Fe-18Cr-10Mn-4Ni austenitic heat-resistant steel

Fig. 2  The new steel shows excellent resistance to the mass gain and the spallation of oxide layer.

Fig. 3  Schematic diagram of oxidation mechanism of new austenitic heat-resistant steel

　　Fig. 4  A ferrite transformation layer with sufficient Cr content is formed on the subsurface of the new austenitic heat-resistant steel to obtain excellent oxidation resistance (Fig. 4f). The wave-shaped oxide layer/substrate interface formed by oxidized particles plays the role of pinning effect and improves the resistance to spallation (Fig. 4b and 4d).

　　Paper information:

　　Liu, T. L., Zheng, K. H., Lin, Y. F., & Luo, Z. C. (2021). Effect of second-phase particles on the oxidation behaviour of a high-manganese austenitic heat-resistant steel. Corrosion Science, 182, 109284.

　　Original paper link:

　　https://www.sciencedirect.com/science/article/pii/S0010938X21000500