Towards sustainable steam turbine systems: emerging materials and characterization frontiers- a comprehensive review

Steam turbines remain central to large-scale electricity generation globally, with continued improvements in efficiency relying heavily on advances in high-temperature materials and their qualification for increasingly demanding operating conditions. This review examines the evolution of steam turbine materials from conventional Cr–Mo–V steels to advanced ferritic–martensitic steels and Ni-based superalloys developed for ultra-supercritical (USC) and advanced ultra-supercritical (A-USC) applications (700–725 °C, 30–31 MPa). Emphasis is placed on the microstructure–property relationships governing creep strength, fatigue resistance, oxidation behaviour, and long-term degradation. Emerging material characterization techniques, including advanced microscopy, diffraction-based methods, and data-driven approaches, are critically assessed for their role in understanding degradation and supporting material qualification. Environmental degradation mechanisms, rotor-scale testing methodologies, additive manufacturing and challenges associated with large-component manufacturing and life prediction are also reviewed. By synthesizing mechanistic understanding with plant-level efficiency requirements, this review outlines critical knowledge gaps and proposes future directions in alloy design, failure redressal, surface engineering, and materials development for high steam temperatures (> 600 °C). Finally, sustainability benefits arising from higher plant efficiency (> 45%), extended component life, and reduced emissions are discussed, along with key research priorities required for the digitalization and commercial deployment of modern steam turbine technologies.