Research on the radial microstructure evolution behavior of DC53/42CrMo composite tube billets produced by centrifugal casting method

Bimetallic composite cutter rings have emerged as a pivotal direction in the development of high-performance TBM disc cutter rings, owing to their flexible design of inner and outer layer materials that effectively satisfies the stringent requirement of "hard exterior and tough interior" during hard rock tunneling. This study proposes a new high-efficiency centrifugal casting and ring rolling forming process for composite cutter rings, specifically investigating the elemental distribution, microstructure variation, and performance of centrifugal casting DC53/42CrMo bimetallic cast tube billets. The results indicate that the bimetallic transition zone between the inner and outer layers of the bimetallic cast tube billets is free from defects such as slag inclusions, cracks, and shrinkage cavities, exhibiting sound metallurgical bonding. The composition distribution within each of the DC53 and 42CrMo layers is relatively uniform. Based on thermodynamics and kinetics, it is proposed that the degree of radial segregation of carbides during centrifugal casting is governed not only by density differences but also by kinetic factors, such as the solid fraction at the onset of precipitation. Furthermore, the mechanism underlying the anomalously low solute element content in the bimetallic transition zone is proposed based on elemental distribution characteristics. The radial hardness distribution of the bimetallic cast tube billets suggests that the cooling rate and matrix composition, particularly the carbon content, are the fundamental factors influencing the as-cast hardness of the cutter ring. This work provides a theoretical basis for the centrifugal casting of high-performance bimetallic composite cutter rings.