Evaluation of post-treatments of novel hot-work tool steel manufactured by laser powder bed fusion for aluminum die casting applications

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 800; p. 140305
• Main Authors: Vilardell, A.M., Hosseini, S.B., Åsberg, M., Dahl-Jendelin, A., Krakhmalev, P., Oikonomou, C., Hatami, S.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 07-01-2021; Elsevier BV
• Subjects: 3D printers; Aluminum; Aluminum coated steel; Aluminum die casting; Aluminum nitride; Conventional methods; Crack initiation; Crack propagation; Cracks; Die casting; Die casting dies; Die casting machines; Die casting process; Dies; Fatigue failure; Fatigue testing; Fatigue tests; Fracture mechanics; Fracture toughness; Geometric complexity; Hardness; Heat treating; Heat treatment; Hot isostatic pressing; Hot work tool steels; Hot working; Hot-work tool steel; Impact strength; Iron and steel making; Laser powder bed fusion; Materials Science; Materialvetenskap; Near net shaping; Nitriding; Nucleation; Powder beds; Production methods; Softening; Steel making; Surface hardness; Tempered martensite; Tensile strength; Tensile testing; Thermal fatigue; Thermal fatigue cracks; Tool steel; Ultimate tensile strength; Yield strength; Laser powder bed fusion; Nitriding; Hot-work tool steels; Heat treatment; Thermal fatigue; Die casting
• ISSN: 0921-5093; 1873-4936; 1873-4936
• DOI: 10.1016/j.msea.2020.140305

Additive manufacturing is a good alternative to conventional methods for the production of near net shape geometries with high geometric complexity shorter lead times, being a good option for the manufacturing of dies for die casting process. In this research, a novel hot-work tool steel for aluminum die casting applications manufactured by laser powder bed fusion was investigated. As-built and stress-relieved (AS-B + SR) state was established and used as the reference condition, and subsequent post-treatments were added and compared to the reference condition. Test parts were evaluated using tensile, impact, hardness and thermal fatigue testing. Compared to the reference condition, heat treatment (HT), significantly increased the hardness, yield and ultimate tensile strengths of the material, due to the obtained tempered martensite microstructure. Hot isostatic pressing (HIP) prior to HT significantly increased the impact toughness and ductility, and slightly increased the yield and ultimate tensile strength values compared to the HT condition. The addition of nitriding treatment after HT, without intermedium HIP step, resulted in the highest surface hardness and lowest impact toughness. Thermal fatigue was mostly affected by the hardness and the softening of the material during the thermal fatigue testing. Results showed that a high surface hardness resulted in a higher thermal fatigue crack nucleation, meanwhile conditions with a high softening during thermal fatigue performance resulted in a higher crack propagation.