Research about the microcrack mechanisms in molybdenum and corresponding suppression strategies during laser additive manufacturing process

Abstract

In this study, the mechanism of microcracks in the laser powder bed fusion of molybdenum was analyzed, and the corresponding solutions were proposed. Through specially designed single-track experiment and finite element simulation analyses, we found that thermal stress was the main cause of cracking during the laser powder bed fusion process. The cracks were generated almost synchronously with the laser scanning process, and thus optimizing the process parameters alone could not inhibit the occurrence of cracks. Herein, alloying strategy was proposed and proved to be an effective way to solve the cracking problems. Specifically, by adding Cr and Ti elements, the high-temperature mechanical properties of Mo were improved through solid solution strengthening mechanism, hence the thermal stress induced cracking was suppressed effectively. In addition, according to the thermodynamic calculations, it was found that Cr and Ti had an inhibitory effect on the segregation of impurity at the grain boundaries and this conduce to improve the strength as well.