The Possibilities of the Retained Austenite Reduction on Tool Steels

Abstract

The retained austenite induces a great deal of internal stress in the steel, often manifesting itself as cracks. Retained austenite also have a negative effect on dimensional stability of the steel components. In tool steels retained austenite is considered to be highly detrimental and is the cause of many application failures. Tool steels must be able to attain high hardness, high compressive strength, good toughness to be suitable for forming of advanced high-strength steels. The high alloying elements content tool steels result is low martensite start and martensite finish temperatures. As a result, the transformation of austenite to martensite does not go to completion when quenching to room temperature. In this work the effects of tempering and cryogenic treatment were investigated for reducing the amount of residual austenite in case of a cold work tool steel and a hot work tool steel. The results showed that in the case of tool steels, during high hardening and three times tempering at high temperatures, the amount of residual austenite was significantly reduced and as a result of cryogenic treatment completely disappeared.

Martensite Transformation in Tool Steels under Isostatic Pressure–Implementation of In-Situ Electrical Resistivity Measurements into a Hot Isostatic Press with Rapid Quenching Technology

“…A steady trend concerning hardness in the as-quenched condition is, however, not visible (Figure 7). Based on these results it can be inferred that stabilization of retained austenite (RA) in the course of a high-pressure heat treatment is not relevant at least for AISI H11, as high amounts of RA would go along with a measurable decrease in hardness [22]. For higher alloyed grades with lower M S temperatures, e.g., high speed steels, a distinct stabilization of retained austenite by integrated HIP treatment can be anticipated.…”