Effect of Heat Treatment on the Microstructure and Mechanical Properties of Nitrogen-Alloyed High-Mn Austenitic Hot Work Die Steel

Abstract

Abstract:In view of the requirements for mechanical properties and service life above 650 • C, a high-Mn austenitic hot work die steel, instead of traditional martensitic hot work die steel such as H13, was developed in the present study. The effect of heat treatment on the microstructure and mechanical properties of the newly developed work die steel was studied. The results show that the microstructure of the high-Mn as-cast electroslag remelting (ESR) ingot is composed of γ-Fe, V(C,N), and Mo 2 C. V(C,N) is an irregular multilateral strip or slice shape with severe angles. Most eutectic Mo 2 C carbides are lamellar fish-skeleton-like, except for a few that are rod-shaped. With increasing solid solution time and temperature, the increased hardness caused by solid solution strengthening exceeds the effect of decreased hardness caused by grain size growth, but this trend is reversed later. As a result, the hardness of specimens after various solid solution heat treatments increases first and then decreases. The optimal combination of hardness and austenitic grain size can be obtained by soaking for 2 h at 1170 • C. The maximum Rockwell hardness (HRC) is 47.24 HRC, and the corresponding austenite average grain size is 58.4 µm. When the solid solution time is 3 h at 1230 • C, bimodality presented in the histogram of the austenite grain size as a result of further progress in secondary recrystallization. Compared with the single-stage aging, the maximum impact energy of the specimen after two-stage aging heat treatment was reached at 16.2 J and increased by 29.6%, while the hardness decreased by 1-2 HRC. After two-stage aging heat treatment, the hardness of steel reached the requirements of superior grade H13, and the maximum impact energy was 19.6% higher than that of superior grade H13, as specified in NADCA#207-2003.

Effect of Heat Treatments on the Microstructure and Wear Resistance of a Modified Hadfield Steel

“…Dissolution of these carbides requires a particular heat treatment (holding at 1000°C to 1100°C and cooling in the water). The obtaining of the enriched austenite free of precipitates at grain boundaries affects positively hardness and wear resistance [16][17][18][19].…”

High-Temperature Deformability of a Fe-Cr-Mn-Ni Austenite Stainless Steel with High Nitrogen and High Carbon Contents

“…The substitution of Ni with Mn and nitrogen has been proven to be successful in the production of austenitic stainless steels. In addition to stabilizing austenitic structures, nitrogen is known to reduce the stacking fault energy of austenitic stainless steels, resulting in a number of beneficial effects such as enhanced strength, fatigue resistance, and impact and fracture resistances [1][2][3][4][5]. Since nickel is known to be an allergen, nickel-less and/or nickel-free stainless steels are expected to be favored, especially for biomedical applications [6].…”

The Relationship Between Oxidation and Thermal Fatigue of Martensitic Hot-Work Die Steels

“…The optimization of heat treatments such as austenitizing and tempering was also attempted to improve high-temperature stability, strength and toughness of the steel [13,24]. Heat treatments were designed to optimize the austenitic grain size, solute content and precipitation [25], increasing hardness and impact toughness [26]. It is reported that proper quenching-partitioning-tempering treatment could improve the fatigue resistance of 20Mn2SiCrNiMo bainite/martensite multiphase steels due to the presence of leaf-shaped bainite and refined retained austenite [27].…”