Thermal Fatigue Properties of H13 Hot-Work Tool Steels Processed by Selective Laser Melting

Abstract

Currently, selective laser melting (SLM) is gaining widespread popularity as an alternative manufacturing technique for complex and customized parts, especially for hot-work and injection molding applications. In the present study, as the major factors for the failure of H13 hot-work die steels during hot-working, thermal fatigue (TF) properties of H13 processed by SLM and a conventional technique were investigated. TF tests (650 °C/30 °C) were conducted on the as-selective laser melted (As-SLMed), thermally treated selective laser melted (T-SLMed), and forged (Forged) H13. Results show that the As-SLMed H13 exhibited the best TF resistance properties among the specimens herein (the shortest total crack length and highest hardness of 687 ± 12 HV5), whereas the Forged H13 exhibited the poorest TF resistance properties (the longest total crack length and lowest hardness of 590 ± 11 HV5) after TF tests. TF resistance properties were closely related to the initial and final hardness. Further microstructural investigations revealed that the typical cell-like substructures, increased amount of retained austenite, and most importantly, refined grain size were the main reasons for the improved TF resistance properties in the As-SLMed H13 compared to the Forged counterparts.

Ultrastrong and ductile synergy of additively manufactured H13 steel by tuning cellular structure and nano-carbides through tempering treatment

“…Fig. 10b shows a comparison of tensile strength of H13 steel manufactured by different techniques, including conventional casting methods [18,41,42], SLM [ [1,2,23,28,43]] and SLM þ heat treatment [28,34,41]in both other literatures and this study. Obviously, the ST-600 and ST-700 samples showed a good balance between strength and ductility.…”

“…The as-SLMed H13 is usually featured by fine primary grains, cellular structures and carbides [10,17]. However, the resulting mechanical properties are normally unsatisfactory due to the high-volume fraction of retained austenite (15e20%) [15,18] and residual stresses (~1420 MPa) [12,19,20]. Moreover, the ductility is inferior to that obtained by conventional manufacturing techniques [21e23].…”

Influence of Tempering Temperature and Time on Microstructure and Mechanical Properties of Additively Manufactured H13 Tool Steel

“…Commercial forged H13 steels have been reported to have UTS of 1200–1590 MPa, elongation of 6–9%, and hardness of 46–50 HRC [ 22 , 36 , 37 , 38 ]. Regarding these mechanical properties of commercially forged H13, additively manufactured H13 using the LPBF process did not show significant differences in this study.…”

“…They revealed that the direct tempering of H13, showing more dispersal of carbide, resulted in a lower thermal softening than conventional post-HT of H13, which includes a solution treatment before the tempering. Wang et al [ 22 ] investigated the effect of a double-tempering HT on the thermal fatigue properties of H13 manufactured using a selective laser melting (SLM) process, which fully melts the metal powder. The H13 manufactured using the SLM showed a superior thermal fatigue resistance compared to the forged H13 due to its fine microstructure and higher amount of retained austenite.…”

Microstructures and Mechanical Properties of H13 Tool Steel Fabricated by Selective Laser Melting

“…More importantly, the elongation of as-SLMed H13 is normally lower than that obtained by conventional methods [ 12 , 13 , 14 ]. It was addressed that the high fluctuation of mechanical properties are mainly a response for the different contents of residual austenite [ 15 , 16 ], high residual stresses [ 17 , 18 , 19 ] and defects [ 20 , 21 ].…”