Microstructure and Origin of Hot-Work Tool Steel Fracture Toughness Deviation

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 44; no. 13; pp. 5694 - 5702
• Main Authors: Podgornik, Bojan, Leskovšek, Vojteh
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.12.2013; Springer; Springer Nature B.V
• Subjects: Applied sciences; Characterization and Evaluation of Materials; Chemistry and Materials Science; Exact sciences and technology; Fracture toughness; Fractures; Materials Science; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metallic Materials; Metals. Metallurgy; Microstructure; Nanotechnology; Steel; Structural Materials; Surfaces and Interfaces; Thin Films; Fracture Toughness; High Fracture Toughness; Fatigue Crack; Secondary Carbide; Lower Fracture Toughness; Hot deformation; Mechanical properties; Microstructure; Tool steel; Rupture; Fracture toughness
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-013-1921-6

Dies and tools used in hot metal forming are exposed to elevated temperatures and high contact pressures, and therefore to wear and fatigue. Fracture toughness is thus one of the main material properties used when selecting and optimizing heat treatment of tools. However, fracture toughness data alone is not sufficient and need to be supported by other material properties and features. The aim of the present research work was to correlate fracture toughness properties of hot-work tool steel, especially its variation to the local microstructure, microhardness, and composition and to establish methodology for proper evaluation of tool steel’s fracture toughness. Research was performed on H11-type hot-work tool steel specimens, heat treated under the same conditions but displaying greatly different fracture toughness. Results show that the presence of any weak point, either in a form of non-metallic inclusions and/or large undissolved eutectic carbide clusters, located in the region of positive segregation with high microhardness will lead to considerable reduction in fracture toughness.