Crystallisation Route of Tin-Based Bearing Alloys in Static and Centrifugal Casting

In this paper, the authors analyse the crystallisation of bearing alloys used for heavy-duty plain bearings. The composition consists of tin, antimony, copper, and small additions of modifying elements. All the constituents are present in various amounts in the matrix and primary intermetallic phases. Due to a wide range of solidification factors, like cooling rate and pressure, these can change the sequence of crystallisation or lead to segregation of structural components. The present study compares the equilibrium crystallisation of the studied alloys, calculated with Thermo-Calc software, with the experimental results. Data was acquired using the TDA method for alloys poured into standard sand cups as well as into metallic probes of the same geometry, in cold and heated states. The final experiment was conducted with crystallisation analysis during centrifugal casting of alloys poured into steel and cast-iron model bearing housings with different initial temperatures. The authors made an effort to compare and describe the route of crystallisation of the alloys and the influence of the technological process on their structures. The studies also included an extended examination of the structure of the alloys and phenomena connected with the possible segregation of structural components using SEM and optical microscopy.