Effect of sintering temperature on microstructure and properties of Co-Cr alloys fabricated by vat photopolymerization 3D printing technology

In this study, dense and evenly microstructured Co-Cr alloy blocks were prepared for the first time by degreasing and sintering after vat photopolymerization three-dimensional (3D) printing, and the effect of sintering temperature on the alloy microstructure was investigated. The results showed that the Co-Cr alloy sintered at 1180 degrees C had a low density with many pores in its microstructure. Increasing the sintering temperature from 1200 degrees C to 1240 degrees C improved the density and uniformity of the microstructure, and the grain size in the Co-Cr alloy increased with an increasing sintering temperature. Furthermore, the carbon content of the Co-Cr alloy increased after sintering because of the breakage of C-C and C-H bonds in the binder, which also changed the types of phases formed in the Co-Cr alloy. After sintering at 1180 degrees C, the phases in the Co-Cr alloy were mainly gamma(Co-fcc), 8 (Co-hcp), a, mu, and M23C6 carbides. With an increase in the temperature and carbon content, the phases in the Co-Cr alloy transformed to gamma (Co-fcc), M23C6, M7C3, and M6C. Additionally, the hardness of the Co-Cr alloy after sintering at 1180 degrees C was 493.5 f 19.6 HV, which is lower than that of the samples sintered at 1200 degrees C (549.1 f 14.8 HV), 1220 degrees C (542 f 13.5 HV), and 1240 degrees C (547 f 14.3 HV), whereas it changed slightly from 1200 to 1240 degrees C. The results reveal that the microstructure and properties of Co-Cr alloy blocks prepared by vat photopolymerization 3D printing technology are strongly related to degreasing and sintering processes.