Characteristics and stability of oxide + carbonitride in H13 steel at 1250 °C

The morphology, size, quantity, and composition of complex oxide + carbonitride in H13 steel held at 1250 °C for 5, 10, and 15 h were determined. The results show that the ratio and number of complex carbonitrides with cores in H13 steel are gradually increased when holding at 1250 °C compared with those in the original H13 steel, and the core size increases. There are one or more oxide cores in (Ti_x,V_1−x)(C_y,N_1−y), including xCaO·zAl₂O₃, xCaO·yMgO·zAl₂O₃, and CaO after holding at 1250 °C, in addition to MgO·Al₂O₃ and Al₂O₃ in the original steel. The equilibrium temperature for (Ti_x, V_1−x)(C_y,N_1−y) precipitation at the solidification front and decomposition in the solid state was theoretically analyzed, which was affected by the x value and the product of Ti and N contents in H13 steel. Meanwhile, the composition of (Ti_x,V_1−x)(C_y,N_1−y) is influenced by the oxide cores. It is convinced that (Ti_x,V_1−x)(C_y,N_1−y) with oxide cores has a higher stability, especially for oxides with a high Al₂O₃ content. Heat treatment at high temperature facilitates a more reasonable analysis of oxide + carbonitride, and the generation mechanism of oxide + carbonitride was discussed.