Development of Creep-Resistant and Oxidation-Resistant Austenitic Stainless Steels for High Temperature Applications

Abstract

Austenitic stainless steels are cost-effective materials for high-temperature applications if they have the oxidation and creep resistance to withstand prolonged exposure at such conditions. Since 1990, Oak Ridge National Laboratory (ORNL) has developed advanced austenitic stainless steels with creep resistance comparable to Ni-based superalloy 617 at 800-900°C based on specially designed ''engineered microstructures'' utilizing a microstructure/composition database derived from about 20 years of radiation effect data on steels. The wrought high temperature-ultrafine precipitate strengthened (HT-UPS) steels with outstanding creep resistance at 700-800°C were developed for supercritical boiler and superheater tubing for fossil power plants in the early 1990s, the cast CF8C-Plus steels were developed in 1999-2001 for land-based gas turbine casing and diesel engine exhaust manifold and turbocharger applications at 700-900°C, and, in 2015-2017, new Al-modified cast stainless steels with oxidation and creep resistance capabilities up to 950-1000°C were developed for automotive exhaust manifold and turbocharger applications. This article reviews and summarizes their development and their properties and applications.

Corrosion resistance and microstructural stability of austenitic Fe–Cr–Al–Ni model alloys exposed to oxygen-containing molten lead

“…The exploration and the development of AFA steels have been focused so far mainly on the replacement of Ni-base alloys or austenitic steels in different environments [69,78,79,82,[88][89][90][91][92][93][94]. However, the direct transfer of AFA steels engineering-knowhow, related to these environments, to applications in HLMs is questionable, because of the additional physical and chemical interactions implied by the contact with such media.…”

“…Based on the Ni content and the targeted alumina formation temperature range, the AFA steels are classified into three categories: (i) high Ni-content (30-35 wt.%), with relatively high strength, for applications in the temperature range ∼ 750-850°C, (ii) standard Ni-content (20-25 wt.%) for applications in the temperature range ∼ 750-950°C and (iii) low Ni-content (12-15 wt.%), for the temperature range ∼ 650-700°C [72]. The corrosion tests of the AFA steel grades, performed in air and air + water vapor, have shown their excellent corrosion behaviour especially at higher temperatures (>800°C), due to the formation of an alumina scale [69,78,79,82,88]. However, tests performed at lower temperatures (550°C) in air, revealed the formation of only Fe-based oxide without traces of alumina [89].…”

Microstructure and Mechanical Properties of 4Al Alumina-Forming Austenitic Steel after Cold-Rolling Deformation and Annealing

“…As a high-temperature alloy, since it was firstly developed at Oak Ridge National Laboratory (ORNL) in 2007, alumina-forming austenitic heat-resistant (AFA) steel hopefully, instead of the ferritic steel and nickel-based alloy, has enormous potential to be applied to ultra-supercritical thermal power plants [1][2][3]. AFA steel is very promising for application in aggressive high-temperature steam in excess of 700 • C to promote energy conversion efficiency owing to the considerable creep life and excellent oxidation resistance of AFA steel.…”

Composition Optimum Design and Strengthening and Toughening Mechanisms of New Alumina-Forming Austenitic Heat-Resistant Steels

“…Due to the increasing demands for electric power around the world, the development of clean and efficient coal-fired thermal power generation with lower fuel costs and lower emissions is being pursued in the medium-to long-term future [1]. The efficiency of electricity generation is positively related to the steam conditions (temperatures and pressures) [2]. However, increases in operating temperature and pressure present many challenges for materials with both excellent oxidation and mechanical properties.…”