Method to Improve Steel Creep Strength by Alloy Design and Heat Treatment

Method to Improve Steel Creep Strength by Alloy Design and Heat Treatment

Research is active on the patent pending technology titled "Creep Resistant High Temperature Martensitic Steel.” This technology is available for licensing and/or further collaborative research from the U.S. Department of Energy’s National Energy Technology Laboratory.
Abstract: 
The operating efficiency of coal-fired power plants is directly related to combustion system temperature and pressure. Incorporation of ultrasupercritical (USC) steam conditions into new or existing power plants can increase efficiency and reduce coal utilization, while reducing carbon dioxide emissions. Traditional materials used in USC power plants do not possess the creep capability for long-term use above 610 °C. Under USC conditions, the 9% chromium (Cr) martensitic steels exhibit shortened component functional lifespan or require the use of thicker components or the substitution of more costly austenitic stainless steels or nickel-base alloys, resulting in increased costs. As a consequence, advanced steels and manufacturing processes are needed to develop materials for use in these extreme conditions. The operating efficiency of coal-fired power plants is directly related to combustion system temperature and pressure. Incorporation of ultrasupercritical (USC) steam conditions into new or existing power plants can increase efficiency and reduce coal utilization, while reducing carbon dioxide emissions. Traditional materials used in USC power plants do not possess the creep capability for long-term use above 610 °C. Under USC conditions, the 9% chromium (Cr) martensitic steels exhibit shortened component functional lifespan or require the use of thicker components or the substitution of more costly austenitic stainless steels or nickel-base alloys, resulting in increased costs. As a consequence, advanced steels and manufacturing processes are needed to develop materials for use in these extreme conditions. The approach builds upon existing alloy design fundamentals but makes use of computational materials design strategies both in the selection of steel target chemistries suitable for high temperature creep strength and heat treatment, as well as the homogenization heat treatment schedule to insure uniformity of elements within the matrix. The resulting steel is similar to existing steels in terms of general microstructure features, but to date has shown creep capability twice that of existing commercial 9% Cr martensitic steels.
Benefits: 
Excellent and consistently achievable tensile mechanical properties -Improved creep resistance under high temperature AUSC steam conditions -Increased creep strength does not impact steel fabrication processing -Extended functional lifespan of boiler and steam turbine components -Applicable to both wrought/forged products as well as thick-wall castings
applications: 
Patent Number: 
Patent Issued
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