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.

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.

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.

Sign in / Sign up

Export Citation Format

Share Document