Hot Deformation Behavior and Microstructural Evolution of a Nickel-Free Austenitic Steel with High Nitrogen Content
- PDF / 791,471 Bytes
- 7 Pages / 593.972 x 792 pts Page_size
- 100 Downloads / 256 Views
DUCTION
NICKEL-FREE high nitrogen stainless steels (HNSs) are the material of choice for medical applications.[1–3] Nitrogen improves especially pitting and stress-corrosion cracking resistance and has a large potential for austenite stabilization.[4–6] In addition to these advantages, nitrogen alloying can be an alternative to the high cost of nickel alloying.[7,8] It is also well known nickel may cause allergy and cancer.[4] Corrosion behavior, and mechanical and tribological properties of nickel-free HNSs have been studied intensively in recent years.[9–12] The blood compatibility of nickel-free HNS is better compared with 317L stainless steel.[9] Nickel-free HNSs have also higher fatigue limits and improved tribological properties.[10,11] Potentially, nickel-free HNS can be used as a reliable substitute to the conventional medical stainless steels.[12] The occurrence of r-phase and Cr nitrides may reduce the fracture toughness and corrosion resistance.[6] Precipitates might affect also high-temperature properties. A severe problem of HNSs is the susceptibility to cracking during hot working.[13,14] Lack of data related to hot deformation processes and phase transformations during heating and thermomechanical treatment restricts the use of HNSs to a large extent.[15] In current study, microstructural and deformation characteristics at high temperatures were investigated for grade X13CrMnMoN18-14-3 high nitrogen steel. Thermodynamic calculations and homogenization annealing experiments were performed to determine ERSOY ERISIR, Assistant Professor, is with the Department of Metallurgical and Materials Engineering, Kocaeli University, Kocaeli, Turkey, and also with the Department of Ferrous Metallurgy, RWTH Aachen University, Aachen, Germany. Contact e-mail: eerisir@ gmail.com ULRICH PRAHL, Group Leader, and WOLFGANG BLECK, Professor, are with the Department of Ferrous Metallurgy, RWTH Aachen University. Manuscript submitted May 30, 2011. METALLURGICAL AND MATERIALS TRANSACTIONS A
phase transformations and precipitations. A simulation of hot deformation was performed via hot tensile and compression tests at typical deformation temperatures ranging from 1173 K to 1573 K (900 °C to 1300 °C).
II.
EXPERIMENTAL PROCEDURE
The chemical composition of the austenitic grade X13CrMnMoN18-14-3 high nitrogen steel is given in Table I. Microstructure of the 400-mm square ingots consists of austenite and Cr2N at grain boundaries, as shown in Figure 1. The hot tensile and compression samples, in Figure 2, were machined from the ingots and pre-annealed in a furnace to develop a forging industry-close surface quality. The pre-annealing was performed at 1423 K (1150 °C) for 2 hours under a gas mixture of 5 vol pct N2 and 95 vol pct CO2, which was followed by cooling in furnace. The calculations were performed by the Thermo-Calc software using the TCS Steel Database TCFE5.[16,17] The Thermo-Calc software calculates the minimum Gibbs free energy for the most stable set of the considered phases using functions fitted to various experim
Data Loading...
