Accelerated Oxidation of Type 347 Stainless Steel Primary Surface Recuperators Operating Above 600°C

2007 ◽  
Author(s):  
Wendy J. Matthews ◽  
Karren L. More ◽  
Larry R. Walker
Keyword(s):  
Stainless Steel ◽  
Water Vapor ◽  
Stainless Steels ◽  
National Laboratory ◽  
Austenitic Stainless Steels ◽  
Operating Conditions ◽  
Accelerated Oxidation ◽  
Oak Ridge ◽  
Compositional Changes ◽  
Operating Temperatures

Type 347 stainless steel has traditionally been used in the manufacture of microturbine primary surface recuperators. It has been established during the past few years that the water vapor present in the microturbine exhaust gas causes accelerated oxidation of austenitic stainless steels at operating temperatures above ∼600°C (∼1110°F), which has resulted in the replacement of austenitic stainless steels with more highly alloyed Fe-based alloys and Ni-based alloys in microturbine recuperators. The effect of water vapor on type 347 stainless steel primary surface recuperators has been studied extensively by Capstone Turbine Corporation in collaboration with Oak Ridge National Laboratory. Several recuperators exposed in a Capstone C60 MicroTurbine™ under different steady-state and cyclic operating conditions, have been microstructurally characterized. Evaluation of surface oxide scale formation and associated compositional changes has been carried out on representative sections from recuperators with operating lives ranging from ∼2,000–15,000 hours. Results from the microstructural and compositional analyses of the engine-tested recuperators illustrate the progression of accelerated oxidation of type 347 stainless steel at recuperator operating temperatures above 600°C.

Comparison of Three Microturbine Primary Surface Recuperator Alloys

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Wendy J. Matthews ◽  
Karren L. More ◽  
Larry R. Walker
Keyword(s):  
Stainless Steel ◽  
Water Vapor ◽  
Oxidation Resistance ◽  
National Laboratory ◽  
Oak Ridge ◽  
Alloy Type ◽  
Oak Ridge National Laboratory ◽  
Oxidation Resistant ◽  
Compositional Changes ◽  
Alloy Depletion

Extensive work performed by Capstone Turbine Corporation, Oak Ridge National Laboratory, and various others has shown that the traditional primary surface recuperator alloy, type 347 stainless steel, is unsuitable for applications above 650°C(∼1200°F). Numerous studies have shown that the presence of water vapor greatly accelerates the oxidation rate of type 347 stainless steel at temperatures above 650°C(∼1200°F). Water vapor is present as a product of combustion in the microturbine exhaust, making it necessary to find replacement alloys for type 347 stainless steel that will meet the long life requirements of microturbine primary surface recuperators. It has been well established over the past few years that alloys with higher chromium and nickel contents than type 347 stainless steel have much greater oxidation resistance in the microturbine environment. One such alloy that has replaced type 347 stainless steel in primary surface recuperators is Haynes Alloy HR-120 (Haynes and HR-120 are trademarks of Haynes International, Inc.), a solid-solution-strengthened alloy with nominally 33 wt % Fe, 37 wt % Ni and 25 wt % Cr. Unfortunately, while HR-120 is significantly more oxidation resistant in the microturbine environment, it is also a much more expensive alloy. In the interest of cost reduction, other candidate primary surface recuperator alloys are being investigated as possible alternatives to type 347 stainless steel. An initial rainbow recuperator test has been performed at Capstone to compare the oxidation resistance of type 347 stainless steel, HR-120, and the Allegheny Ludlum austenitic alloy AL 20–25+Nb (AL 20–25+Nb is a trademark of ATI Properties, Inc. and is licensed to Allegheny Ludlum Corporation). Evaluation of surface oxide scale formation and associated alloy depletion and other compositional changes has been carried out at Oak Ridge National Laboratory. The results of this initial rainbow test will be presented and discussed in this paper.

Developing New Cast Austenitic Stainless Steels With Improved High-Temperature Creep Resistance

2007 ◽  
Author(s):  
Philip J. Maziasz ◽  
John P. Shingledecker ◽  
Neal D. Evans ◽  
Michael J. Pollard
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Creep Strength ◽  
Stainless Steels ◽  
Creep Resistance ◽  
National Laboratory ◽  
Austenitic Stainless Steels ◽  
Alloy Development ◽  
Oak Ridge ◽  
Wide Range

Oak Ridge National Laboratory (ORNL) and Caterpillar have recently developed a new cast austenitic stainless steel, CF8C-Plus, for a wide range of high-temperature applications, including diesel exhaust components and turbine casings. The creep-rupture life of the new CF8C-Plus is over ten times greater than that of the standard cast CF8C stainless steel, and the creep-strength is about double. Another variant, CF8C-Plus Cu/W has been developed with even more creep strength at 750–850°C. The creep-strength of these new cast austenitic stainless steels is close to that of Ni-based superalloys like 617. CF8C-Plus steel was developed in about 1.5 years using an “engineered microstructure” alloy development approach, which produces creep resistance based on formation of stable nano-carbides (NbC) and prevention of deleterious intermetallics (sigma, Laves). CF8C-Plus steel won a 2003 R&D 100 Award, and to date, over 32,000 lb have been produced in various commercial component trials. The current commercialization status of the alloy is summarized.

Comparison of Three Microturbine Primary Surface Recuperator Alloys

2009 ◽  
Author(s):  
Wendy J. Matthews ◽  
Karren L. More ◽  
Larry R. Walker
Keyword(s):  
Stainless Steel ◽  
Water Vapor ◽  
Oxidation Resistance ◽  
National Laboratory ◽  
Oak Ridge ◽  
Alloy Type ◽  
Oak Ridge National Laboratory ◽  
Oxidation Resistant ◽  
Compositional Changes ◽  
Alloy Depletion

Extensive work performed by Capstone Turbine Corporation, Oak Ridge National laboratory, and various others has shown that the traditional primary surface recuperator alloy, type 347 stainless steel, is unsuitable for applications above 650°C (∼1200°F). Numerous studies have shown that the presence of water vapor greatly accelerates the oxidation rate of type 347 stainless steel at temperatures above 650°C (∼1200°F). Water vapor is present as a product of combustion in the microturbine exhaust, making it necessary to find replacement alloys for type 347 stainless steel that will meet the long life requirements of microturbine primary surface recuperators. It has been well established over the past few years that alloys with higher Chromium and Nickel contents than type 347 stainless steel have much greater oxidation resistance in the microturbine environment. One such alloy that has replaced type 347 stainless steel in primary surface recuperators is Haynes Alloy HR-120, a solid-solution-strengthened alloy with nominally 33 wt.% Fe, 37 wt.% Ni and 25 wt.% Cr. Unfortunately, while HR-120 is significantly more oxidation resistant in the microturbine environment, it is also a much more expensive alloy. In the interest of cost reduction, other candidate primary surface recuperator alloys are being investigated as possible alternatives to type 347 stainless steel. An initial rainbow recuperator test has been performed at Capstone to compare the oxidation resistance of type 347 stainless steel, HR-120 and the Allegheny Ludlum austenitic alloy AL 20-25+Nb. Evaluation of surface oxide scale formation and associated alloy depletion and other compositional changes has been carried out at Oak Ridge National Laboratory. The results of this initial rainbow test will be presented and discussed in this paper.

High Temperature Performance of Cast CF8C-Plus Austenitic Stainless Steel

2010 ◽  
Author(s):  
Philip J. Maziasz ◽  
Bruce A. Pint
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
High Temperature ◽  
Austenitic Stainless Steel ◽  
Gas Turbines ◽  
National Laboratory ◽  
Austenitic Stainless Steels ◽  
Medium Size ◽  
Temperature Oxidation ◽  
Oak Ridge

Covers and casings of small to medium size gas turbines, can be made from cast austenitic stainless steels, including grades such as CF8C, CF3M, or CF10M. Oak Ridge National Laboratory (ORNL) and Caterpillar have developed a new cast austenitic stainless steel, CF8C-Plus, that is a fully-austenitic stainless steel, based on additions of Mn and N to the standard Nb-stabilized CF8C steel grade. The Mn addition improves castability, as well as increasing the alloy solubility for N, and both Mn and N act synergistically to boost mechanical properties. CF8C-Plus steel has outstanding creep-resistance at 600°–900°C, which compares well with Ni-based superalloys like alloys X, 625, 617 and 230. CF8C-Plus also has very good fatigue and thermal fatigue resistance. It is used in the as-cast condition, with no additional heat-treatments. While commercial success for CF8C-Plus has been mainly for diesel exhaust components, this steel can also be considered for gas-turbine and microturbine casings. The purpose of this paper is to demonstrate some of the mechanical properties and update the long-term creep-rupture data, and to present new data on the high-temperature oxidation behavior of these materials, particularly in the presence of water vapor.

The Oxidation of Austenitic Stainless Steel Foils in Humidified Air

2001 ◽  
Author(s):  
James M. Rakowski
Keyword(s):  
Stainless Steel ◽  
Water Vapor ◽  
Elevated Temperatures ◽  
Austenitic Stainless Steels ◽  
Breakaway Oxidation ◽  
Accelerated Oxidation ◽  
Time Required ◽  
Humidified Air ◽  
Stainless Steel Foils ◽  
Steel Foils

Austenitic stainless steels form a protective external chromium oxide scale when exposed to elevated temperatures in air. Laboratory testing of thin stainless steel foil specimens demonstrates that the presence of water vapor decreases the time required for breakaway oxidation to occur. Accelerated oxidation begins after the end of an incubation period, the length of which is affected by the amount of water vapor present. Significant changes in scale microstructure accompany the transition from parabolic to accelerated oxidation.

Austenitic Stainless Steels and Alloys With Improved High-Temperature Performance for Advanced Microturbine Recuperators

2004 ◽  
Author(s):  
Philip J. Maziasz ◽  
Bruce A. Pint ◽  
John P. Shingledecker ◽  
Karren L. More ◽  
Neal D. Evans ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Stainless Steels ◽  
Gas Turbines ◽  
National Laboratory ◽  
Austenitic Stainless Steels ◽  
Cost Effective ◽  
Department Of Energy ◽  
Similar Data ◽  
Oak Ridge

Compact recuperators/heat-exchangers increase the efficiency of both microturbines and smaller industrial gas turbines. Most recuperators today are made from 347 stainless steel and operate well below 700°C. Larger engine sizes, higher exhaust temperatures and alternate fuels all demand recuperator materials with greater performance (creep strength, corrosion resistance) and reliability than 347 steel, especially for temperatures of 700–750°C. The Department of Energy (DOE) sponsors programs at the Oak Ridge National Laboratory (ORNL) to produce and evaluate cost-effective high-temperature recuperator alloys. This paper summarizes the latest high-temperature creep and corrosion data for a commercial 347 steel with modified processing for better creep resistanc, and for advanced commercial alloys with significantly better creep and corrosion resistance, including alloys NF709, HR120. Similar data are also provided on small lab heats of several new ORNL modified stainless steels.

scholarly journals High-Temperature Oxidation Resistance of Alumina-Forming Austenitic Stainless Steels Optimized by Refractory Metal Alloying

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 213
Author(s):  
Shuqi Zhang ◽  
Dandan Dong ◽  
Qing Wang ◽  
Chuang Dong ◽  
Rui Yang
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Stainless Steels ◽  
High Temperature Oxidation ◽  
National Laboratory ◽  
Austenitic Stainless Steels ◽  
Alloying Elements ◽  
Temperature Oxidation ◽  
Oak Ridge ◽  
Al2o3 Particles

Alumina-forming austenitic stainless steels are known for their superior high-temperature oxidation resistance. Following our previous work that solved the matching of major alloying elements in their specific 16-atom cluster formula, we here focus on the 800 °C air-oxidation resistance of 0.08 wt. % C alloy series satisfying cluster formula [(Al0.89Si0.05NbxTa0.06−x)-(Fe11.7−yNiyMn0.3)]Cr3.0−z(Mo,W)z, x = 0.03 or 0.06, y = 3.0 or 3.2, z = 0.07 or 0.2, to explore the effect of minor alloying elements Mo, Nb, Ta and W. This cluster formula is established particularly based on alloys which were originally developed by Oak Ridge National Laboratory. All samples are graded as complete oxidation resistance level according to Chinese standard HB 5258-2000, as their oxidation rate and oxidation-peeling mass are generally below 0.1 g/m2 × h and 1.0 g/m2, respectively. In alloys without Ta and W, a Cr2O3-type oxide layer is formed on the surface and Al2O3 particles of sizes up to 4 μm are distributed beneath it. In contrast, in Ta/W-containing alloys, a continuous protective Al2O3 layer is formed beneath the outer Cr2O3 layer, which prevents internal oxidation and provides the lowest weight gain. Instead of internal Al2O3 particles, AlN is formed in Ta/W-containing alloys. The W-containing alloy possesses the thinnest internal nitride zone, indicating the good inhibition effect of W on nitrogen diffusion.

High-Temperature Performance of Cast CF8C-Plus Austenitic Stainless Steel

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
Philip J. Maziasz ◽  
Bruce A. Pint
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
High Temperature ◽  
Austenitic Stainless Steel ◽  
Gas Turbines ◽  
National Laboratory ◽  
Austenitic Stainless Steels ◽  
Medium Size ◽  
Temperature Oxidation ◽  
Oak Ridge

Covers and casings of small to medium size gas turbines can be made from cast austenitic stainless steels, including grades such as CF8C, CF3M, or CF10M. Oak Ridge National Laboratory and Caterpillar have developed a new cast austenitic stainless steel, CF8C-Plus, which is a fully austenitic stainless steel, based on additions of Mn and N to the standard Nb-stabilized CF8C steel grade. The Mn addition improves castability, as well as increases the alloy solubility for N, and both Mn and N synergistically act to boost mechanical properties. CF8C-Plus steel has outstanding creep-resistance at 600–900°C, which compares well with Ni-based superalloys such as alloys X, 625, 617, and 230. CF8C-Plus also has very good fatigue and thermal fatigue resistance. It is used in the as-cast condition, with no additional heat-treatments. While commercial success for CF8C-Plus has been mainly for diesel exhaust components, this steel can also be considered for gas turbine and microturbine casings. The purposes of this paper are to demonstrate some of the mechanical properties, to update the long-term creep-rupture data, and to present new data on the high-temperature oxidation behavior of these materials, particularly in the presence of water vapor.

ALZ 316

Alloy Digest ◽  
1999 ◽  
Vol 48 (8) ◽  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Austenitic Stainless Steel ◽  
Physical Properties ◽  
Tensile Properties ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Heat Treating

Abstract ALZ 316 is an austenitic stainless steel with good formability, corrosion resistance, toughness, and mechanical properties. It is the basic grade of the stainless steels, containing 2 to 3% molybdenum. After the 304 series, the molybdenum-containing stainless steels are the most widely used austenitic stainless steels. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-756. Producer or source: ALZ nv.

ALLOY 0Cr25Ni6Mo3CuN

Alloy Digest ◽  
1998 ◽  
Vol 47 (2) ◽  
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Temperature Performance ◽  
Steel Research ◽  
Oil Refinement

Abstract ALLOY 0Cr25Ni6Mo3CuN is one of four grades of duplex stainless steel that were developed and have found wide applications in China since 1980. In oil refinement and the petrochemical processing industries, they have substituted for austenitic stainless steels in many types of equipment, valves, and pump parts. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on low and high temperature performance, and corrosion resistance as well as forming and joining. Filing Code: SS-706. Producer or source: Central Iron & Steel Research Institute.

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