The Effect of Water Vapor on Cr Depletion in Advanced Recuperator Alloys

2005 ◽  
Author(s):  
Bruce A. Pint
Keyword(s):  
Water Vapor ◽  
Stainless Steels ◽  
Laboratory Testing ◽  
Low Cost ◽  
Austenitic Stainless Steels ◽  
Nodule Formation ◽  
Exhaust Gas ◽  
Operating Lifetime ◽  
Cr Depletion

Durable alloy foils are needed for gas turbine recuperators operating at 650°–700°C. It has been established that water vapor in the exhaust gas causes more rapid consumption of Cr in austenitic stainless steels leading to a reduction in operating lifetime of these thin-walled components. Laboratory testing at 650°–800°C of commercial and model alloys is being used to develop a better understanding of the long-term rate of Cr consumption in these environments. Results are presented for commercial alloys 709, 120 and 625. After 10,000h exposures at 650° and 700°C in humid air, grain boundary Cr depletion was observed near the surface of all these materials. In the Fe-base alloys, 709 and 120, this depletion led to localized Fe-rich nodule formation. This information then can be used to develop low-cost alternatives to currently available candidate materials.

Development of Alumina-Forming Austenitic Alloys for Advanced Recuperators

2009 ◽  
Author(s):  
Bruce A. Pint ◽  
Michael P. Brady ◽  
Yukinori Yamamoto ◽  
Michael L. Santella ◽  
Jane Y. Howe ◽  
...  
Keyword(s):  
Water Vapor ◽  
Gas Turbines ◽  
Laboratory Data ◽  
Austenitic Stainless Steels ◽  
Alumina Scale ◽  
Exhaust Gas ◽  
Alloy Development ◽  
Creep Properties ◽  
New Class

A new class of corrosion- and creep-resistant austenitic stainless steels has been developed for advanced recuperator applications. The Al and Cr contents have been optimized to maintain a fully austenitic composition for creep strength while allowing the formation of a highly-protective external alumina scale at temperatures up to 900°C in the presence of water vapor. Strengthening was achieved via the formation of stable nano-scale MC type carbides and creep properties were comparable to commercially available advanced austenitic stainless steel alloys. These properties are particularly well-suited for thin-walled recuperators for both small and large gas turbines and fuel cells. By forming an alumina scale, long-term problems with Cr evaporation in the presence of water vapor in the exhaust gas are eliminated. Laboratory data are presented from humid air and microturbine exhaust gas to illustrate the oxidation resistance of this class of alloys at 650°–900°C and compared to results for some current commercial alloys. Alloy development is continuing in order to determine the effect of composition on performance over this temperature range.

The Oxidation of Metal Alloy Foils in the Presence of Water Vapor

2003 ◽  
Author(s):  
James M. Rakowski
Keyword(s):  
Water Vapor ◽  
Elevated Temperature ◽  
Chromium Oxide ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Test Results ◽  
Temperature Oxidation ◽  
Chromium Oxide Layer ◽  
Nickel Base

Water vapor can be detrimental to the elevated temperature oxidation resistance of alloys that rely on the formation of a protective chromium oxide layer. The resulting degradation can be significant, particularly when such alloys are in the form of light gauge sheet and strip. Long term test results will be presented for commercially available wrought austenitic stainless steels and for the nickel-base superalloys 625 and HX exposed at 1300°F and 1400°F in environments containing various levels of water vapor.

The Oxidation of Metal Alloy Foils in the Presence of Water Vapor

2004 ◽  
Vol 126 (4) ◽  
pp. 867-873 ◽  
Author(s):  
James M. Rakowski
Keyword(s):  
Water Vapor ◽  
Elevated Temperature ◽  
Chromium Oxide ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Test Results ◽  
Temperature Oxidation ◽  
Chromium Oxide Layer ◽  
Nickel Base

Water vapor can be detrimental to the elevated temperature oxidation resistance of alloys that rely on the formation of a protective chromium oxide layer. The resulting degradation can be significant, particularly when such alloys are in the form of light gauge sheet and strip. Long-term test results will be presented for commercially available wrought austenitic stainless steels and nickel-base superalloys exposed at 1300°F and 1400°F in environments containing various levels of water vapor.

Stainless Steels With Improved Oxidation Resistance for Recuperators

2004 ◽  
Vol 128 (2) ◽  
pp. 370-376 ◽  
Author(s):  
Bruce A. Pint
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Oxidation Resistance ◽  
Stainless Steels ◽  
Lower Cost ◽  
Exhaust Gas ◽  
New Materials ◽  
Excellent Corrosion Resistance ◽  
Gas Environment

New materials are being evaluated to replace type 347 stainless steel in microturbine recuperators operating at higher temperatures in order to increase the efficiency of the microturbine. Commercial alloys 120 and 625 are being tested along with potentially lower cost substitutes, such as Fe-20Cr-25Ni and Fe-20Cr-20Ni. Long-term testing of these materials at 650–700 °C shows excellent corrosion resistance to a simulated exhaust gas environment. Testing at 800 °C has been used to further differentiate the performance of the various materials. The depletion of Cr from foils of these materials is being used to evaluate the rate of attack. Although those alloys with the highest Ni and Cr contents have longer lives in this environment, lower alloyed steels may have sufficient protection at a lower cost.

Contributions of Dr. Sumio Yukawa in the Development of Non-Ductile Failure Prevention Rules in the ASME Code

2008 ◽  
Author(s):  
Hardayal S. Mehta
Keyword(s):  
Elevated Temperature ◽  
Carbon Steel ◽  
Stainless Steels ◽  
Pressure Vessel ◽  
Nickel Alloys ◽  
Ductile Failure ◽  
Austenitic Stainless Steels ◽  
Current Status ◽  
Asme Code

The objective of this paper is to review and highlight the contributions of Dr. Sumio Yukawa in the development of rules for the prevention of non-ductile failure in the ASME Boiler and Pressure Vessel Code. This includes review of his role in the development of WRC-175, Appendix G of Section III, the development of early flaw evaluation rules for carbon steel piping and in the review and evaluation of the toughness of austenitic stainless steels and nickel alloys after long-term elevated temperature exposures. The current status of these activities is briefly described.

Increasing the Upper Temperature Oxidation Limit of Alumina Forming Austenitic Stainless Steels in Air with Water Vapor

2011 ◽  
Vol 75 (5-6) ◽  
pp. 337-357 ◽  
Author(s):  
M. P. Brady ◽  
K. A. Unocic ◽  
M. J. Lance ◽  
M. L. Santella ◽  
Y. Yamamoto ◽  
...  
Keyword(s):  
Water Vapor ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Temperature Oxidation

Development of Fit-for-Purpose Austenitic Stainless Steels With High Polythionic Acid Stress Corrosion Resistance

2017 ◽  
Author(s):  
Takahiro Osuki ◽  
Masahiro Seto ◽  
Hirokazu Okada ◽  
Masayuki Sagara ◽  
Satoshi Matsumoto ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Stainless Steels ◽  
Acid Corrosion ◽  
Acid Stress ◽  
Austenitic Stainless Steels ◽  
Total Acid ◽  
Term Operation ◽  
Stabilization Treatment ◽  
Fit For Purpose

In the process units with Polythionic Acid Stress Corrosion Cracking (PTA-SCC) such as hydrotreater or hydrocracker, the neutralization treatment like soda ash washing and/or PWHT, Post Weld Heat Treatment, are conducted for stabilized austenitic stainless steels of TP321H or TP347H to mitigate the potential of PTA-SCC. 347AP, the proprietary version of Type 347LN, is remarkable for the possibility to save the fabrication and turnaround cost by the elimination of the neutralization treatment and/or PWHT and its reliability to PTA-SCC resistance without PWHT and neutralization was proven by the long-term service experience. However it has not been investigated the difference between 347AP and TP347H for the Stress Relaxation (SR) cracking resistance of welded joint required for the long term operation at elevated temperature. On the other hand, in atmospheric distillation units and vacuum distillation units using the crude containing high Total Acid Number (TAN), the resistances to both Naphthenic Acid Corrosion (NAC) and PTA-SCC are required by elevating the design temperature. Therefore, Fit-for-purpose austenitic stainless steels with high PTA-SCC resistance without stabilization treatment are required for the complicated environment with the variation of temperature, pressure and fluid in petroleum refinery process using the crude containing high S content. In this study, SR cracking susceptibility of 347AP is investigated and it is found that 347AP has lower SR cracking susceptibility than TP347H without stabilization treatment. Next, in order to improve NAC resistance compared with 347AP, the effect of Mo, Cu and W contents to NAC are investigated based on 347AP, and it is clarified that the increase of Mo content greater than 3% is the most effective to improve NAC resistance. Moreover, the conventional welding filler with the similar NAC and PTA-SCC resistances to base metal is investigated, and it is reported that ER NiCrCoMo-1 filler was recommended for the welding fabrication of Fit-for-purpose austenitic stainless steels with high PTA-SCC resistance.

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