Fracture Toughness of a Hot Work Tool Steel Fabricated by Laser‐Powder Bed Fusion Additive Manufacturing. Issue 5 (21st November 2019)

• Record Type: Journal Article
• Authors: Pellizzari, Massimo; Furlani, Sebastiano; Deirmina, Faraz; Siriki, Raveendra; AlMangour, Bandar; Grzesiak, Dariusz
• Other Names: Broeckmann Christoph guestEditor.
• Is Part Of: Steel research international. Volume 91:Issue 5(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-11-21
• Subjects: fracture toughness -- hot work tool steels -- laser powder bed fusion -- microstructure; Steel -- Periodicals; Steel -- Metallurgy -- Periodicals; 669.142
• DOI: 10.1002/srin.201900449
• Languages: English
• ISSNs: 1611-3683

Abstract

Abstract : The fracture toughness of AISI H13 tool steel, additively manufactured by laser powder bed fusion (L‐PBF) technique, is studied. The influence of the building direction on fracture toughness is investigated on small notched bending samples heat treated according to two different thermal cycles, namely, quenching and tempering (QT) and only tempering (T). The notch is electro‐discharge machined parallel (P|| ), perpendicular (P⊥ ), and longitudinal (L) to the building direction. Both heat treatments, even if to a different extent, delete the as‐built (AB) microstructure, producing secondary carbides precipitation in the martensitic matrix. The microstructure of the directly tempered parts is finer than the quenched and tempered ones. The fracture toughness increases moving from P⊥ to P|| . The T samples show a higher apparent fracture toughness in the P||, despite the higher hardness. Secondary cracks formation allows reducing the main crack opening driving force increasing the fracture toughness in P|| samples. This effect is more pronounced in T samples where the stronger precipitation of carbides at the prior melt boundaries promotes secondary cracks. Moreover, in P|| samples the laser tracks act as barriers to crack propagation and as stress dissipators. Abstract : This article deals with the fracture toughness of AISI H13 tool steel, additively manufactured by laser powder bed fusion (L‐PBF). The fracture toughness values measured on small notched bending samples, with notch parallel, perpendicular, and longitudinal to the building direction, after quenching and tempering (QT) and after only tempering (T), evidence limited anisotropy.