Study on typical defects and cracking characteristics of tool steel fabricated by laser 3D printing

Abstract

Porosity and crack are the two most common types of metallurgical defects induced by SLM. It is of great significance to study the porosity and crack defects of H13 tool steel fabricated by SLM for promoting the practical application of this technology in the tool and die manufacturing industry. In this paper, the SLM experiments of H13 tool steel powder were carried out, and H13 tool steel samples were prepared. The microstructure of the as-fabricated samples was characterized by scanning electron microscope (SEM) and optical microscope (OM) to explore the characteristics and formation mechanism of porosity and crack defects in SLM process of H13 tool steel. It can be concluded that there are some metallurgical defects in as-fabricated H13 tool steel samples, such as lack of fusion or poor fusion, pores, and cracks. Most of the cracks are originated from the side edge of the sample, and some branched secondary cracks are induced near the coarse main cracks during the process of cracking along the formed layer to the inside of the sample. And the secondary cracks with small size could prevent the main cracks from continuing to propagate. Furthermore, due to the local stress concentration, some micro-cracks with smaller size are induced near the internal porosity defects.