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Fireside Corrosion USC Steering

Description: Oxy-Fuel Fireside Research goals are: (1) Determine the effect of oxy-fuel combustion on fireside corrosion - (a) Flue gas recycle choice, Staged combustion ramifications, (c) JCOAL Collaboration; and (2) Develop methods to use chromia solubility in ash as an 'ash corrosivity' measurement - (a) Synthetic ashes at first, then boiler and burner rig ashes, (b) Applicable to SH/RH conditions.
Date: September 7, 2011
Creator: Holcomb, G. R. & Tylczak, J.
Partner: UNT Libraries Government Documents Department

Alloys for advanced steam turbines--Oxidation behavior

Description: Advanced or ultra supercritical (USC) steam power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy (DOE) include power generation from coal at 60% efficiency, which would require steam temperatures of up to 760°C. Current research on the oxidation of candidate materials for advanced steam turbines is presented with a focus on a methodology for estimating chromium evaporation rates from protective chromia scales. The high velocities and pressures of advanced steam turbines lead to evaporation predictions as high as 5 × 10-8 kg m-2s-1 of CrO2(OH)2(g) at 760°C and 34.5 MPa. This is equivalent to 0.077 mm per year of solid Cr loss.
Date: October 1, 2007
Creator: Holcomb, G. R.
Partner: UNT Libraries Government Documents Department

Calculation of Reactive-evaporation Rates of Chromia

Description: A methodology is developed to calculate Cr-evaporation rates from Cr2O3 with a flat planar geometry. Variables include temperature, total pressure, gas velocity, and gas composition. The methodology was applied to solid-oxide, fuel cell conditions for metallic interconnects and to advanced-steam turbines conditions. The high velocities and pressures of the advanced steam turbine led to evaporation predictions as high as 5.18 9 10-8 kg/m2/s of CrO2(OH)2(g) at 760 °C and 34.5 MPa. This is equivalent to 0.080 mm per year of solid Cr loss. Chromium evaporation is expected to be an important oxidation mechanism with the types of nickel-base alloys proposed for use above 650 °C in advanced-steam boilers and turbines. It is shown that laboratory experiments, with much lower steam velocities and usually much lower total pressure than found in advanced steam turbines, would best reproduce chromium-evaporation behavior with atmospheres that approach either O2 + H2O or air + H2O with 57% H2O.
Date: April 1, 2008
Creator: Holcomb, G. R.
Partner: UNT Libraries Government Documents Department

Effects of Temperature Gradients and Heat Fluxes on High-Temperature Oxidation

Description: The effects of a temperature gradient and heat flux on point defect diffusion in protective oxide scales were examined. Irreversible thermodynamics were used to expand Fick’s first law of diffusion to include a heat-flux term—a Soret effect. Oxidation kinetics were developed for the oxidation of cobalt and of nickel doped with chromium. Research is described to verify the effects of a heat flux by oxidizing pure cobalt in a temperature gradient at 900 °C, and comparing the kinetics to isothermal oxidation. No evidence of a heat flux effect was found.
Date: April 1, 2008
Creator: Holcomb, G. R.
Partner: UNT Libraries Government Documents Department

Task 1—Steam Oxidation (NETL-US)

Description: The proposed steam in let temperature in the Advanced Ultra Supercritical (A·USC) steam turbine is high enough (760°C) Ihat traditional turbine casing and valve body materials such as ferr;tic/manensitic steels will not suffice due to temperature lim itations of this class of materials. Cast versions of three traditionally wrought Ni-based superalloys (Haynes 263. Haynes 282, and Nimonic 105) were evaluated for use as casing or valve components for the next generation of industrial steam turbines. The full size castings are substantia l: 2-5,000 kg each half and on the order of 100 nun thick. Experimental castings were quite a bit smaller, but section size was retained and cooling rate controlled to produce equi valem microslruclUre •. A multi_step homogenization heat treatment was d~ve loped to better disperse the al loy constituents. These castings were subsequently evaluated by characterizing their microstructure as well as their steam oxidation resistance (al 760 and 800 "C).
Date: May 1, 2010
Creator: Holcomb, G. R.
Partner: UNT Libraries Government Documents Department

Materials Performance in USC Steam

Description: Materials Performance in USC Steam: (1) pressure effects on steam oxidation - unique capability coming on-line; (2) hydrogen evolution - hydrogen permeability apparatus to determine where hydrogen goes during steam oxidation; and (3) NETL materials development - steam oxidation resource for NETL developed materials.
Date: September 7, 2011
Creator: Holcomb, G. R.; Tylczak, J.; Meier, G. H. & Yanar, N. M.
Partner: UNT Libraries Government Documents Department

Materials Performance in USC Steam Portland

Description: Goals of the U.S. Department of Energy's Advanced Power Systems Initiatives include power generation from coal at 60% efficiency, which requires steam conditions of up to 760 C and 340 atm, co-called advanced ultrasupercritical (A-USC) steam conditions. A limitation to achieving the goal is a lack of cost-effective metallic materials that can perform at these temperatures and pressures. Some of the more important performance limitations are high-temperature creep strength, fire-side corrosion resistance, and steam-side oxidation resistance. Nickel-base superalloys are expected to be the materials best suited for steam boiler and turbine applications above about 675 C. Specific alloys of interest include Haynes 230 and 282, Inconel 617, 625 and 740, and Nimonic 263. Further validation of a previously developed chromia evaporation model is shown by examining the reactive evaporation effects resulting from exposure of Haynes 230 and Haynes 282 to moist air environments as a function of flow rate and water content. These two alloys differ in Ti and Mn contents, which may form outer layers of TiO{sub 2} or Cr-Mn spinels. This would in theory decrease the evaporation of Cr{sub 2}O{sub 3} from the scale by decreasing the activity of chromia at the scale surface, and be somewhat self-correcting as chromia evaporation concentrates the Ti and Mn phases. The apparent approximate chromia activity was found for each condition and alloy that showed chromia evaporation kinetics. As expected, it was found that increasing the gas flow rate led to increased chromia evaporation and decreased chromia activity. However, increasing the water content in moist air increased the evaporation, but results were mixed with its effect on chromia activity.
Date: April 26, 2011
Creator: Holcomb, G.R.; Tylczak, J. & Hu, R.
Partner: UNT Libraries Government Documents Department

Task 1 Steam Oxidation (NETL-US)

Description: Some conclusions are: (1) Increased flow rates can lower chromia activity in alloys with Ti and Mn - (a) Reduced chromia activity reduces equilibrium CrO{sub 2}(OH){sub 2}(g) vapor pressures; (2) Model is very sensitive to small decreases in chromia activity at the HP turbine - (a) Upstream partial saturation of the gas phase with CrO{sub 2}(OH){sub 2}(g) can become nearly or fully saturated at the HP turbine, (b) Can radically change breakaway oxidation times from less than a year to never happening; and (3) Thus even small chromia activity reductions from Ti and Mn additions can make evaporation issues self-correcting.
Date: April 28, 2011
Creator: Holcomb, G. R.; Tylczak, J. & R. Hu,
Partner: UNT Libraries Government Documents Department

Steam turbine materials and corrosion

Description: Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of alloys for use in USC systems, with emphasis placed on applications in high- and intermediate-pressure turbines. The list of alloys being examined is discussed, including the addition of new alloys to the study. These include alloy 625, selected because of its use as one of the two alloys used for turbine rotors, valves, casings, blading and bolts in the European AD700 full-scale demonstration plant (Scholven Unit F). The other alloy, alloy 617, is already one of the alloys currently being examined by this project. Other new alloys to the study are the three round robin alloys in the UK-US collaboration: alloys 740, TP347HFG, and T92. Progress on the project is presented on cyclic oxidation in 50% air – 50% water vapor, furnace exposures in moist air, and thermogravimetric analysis in argon with oxygen saturated steam. An update on the progress towards obtaining an apparatus for high pressure exposures is given.
Date: January 1, 2007
Creator: Holcomb, G.R. & Ziomek-Moroz, M.
Partner: UNT Libraries Government Documents Department

Towards Long-Term Corrosion Resistance in FE Service Environments

Description: The push for carbon capture and sequestration for fossil fuel energy production has materials performance challenges in terms of high temperature oxidation and corrosion resistance. Such challenges will be illustrated with examples from several current technologies that are close to being realized. These include cases where existing technologies are being modified—for example fireside corrosion resulting from increased corrosivity of flue gas in coal boilers refit for oxy-fuel combustion, or steam corrosion resulting from increased temperatures in advanced ultra supercritical steam boilers. New technology concepts also push the high temperature corrosion and oxidation limits—for example the effects of multiple oxidants during the use of high CO2 and water flue gas used as turbine working fluids.
Date: October 1, 2010
Creator: Holcomb, G. R. & Wang, P.
Partner: UNT Libraries Government Documents Department

Cast Alloys for Advanced Ultra Supercritical Steam Turbines

Description: Develop advanced coal-based power systems capable of 45–50 % efficiency at <$1,000/kW (in 2002 dollars). Develop technologies for capture and sequestration of CO2 that result in: • <10% increase in the cost of electricity in an IGCC-based plant • <35% increase in the cost of electricity for pulverized coal boilers Demonstrate coal-based energy plants that offer near-zero emissions (including CO2) with multiproduct production
Date: October 1, 2010
Creator: Holcomb, G. R. & Wang, P.
Partner: UNT Libraries Government Documents Department

Countercurrent Gaseous Diffusion Model of Oxidation Through a Porous Coating

Description: A countercurrent gaseous diffusion model was developed to describe oxidation through porous coatings and scales. The specific system modeled involved graphite oxidized through a porous alumina (Al{sub 2}O{sub 3}) overcoat between 570 C (1,058 F) and 975 C (1,787 F). The model separated the porous Al{sub 2}O{sub 3} coating into two gas diffusion regions separated by a flame front, where oxygen (O{sub 2}) and carbon monoxide (CO) react to form carbon dioxide (CO{sub 2}). In the outer region O{sub 2} and CO{sub 2} counterdiffused. In the inner region, CO{sub 2} and CO counterdiffused. Concentration gradients of each gaseous specie in the pores of the Al{sub 2}O{sub 3} were determined, and the oxidation rate was calculated. The model was verified by oxidation experiments using graphite through various porous Al{sub 2}O{sub 3} overcoats. The Al{sub 2}O{sub 3} overcoats ranged in fractional porosity and in average pore radius from 0.077 {micro}m (3.0 x 10{sup -6} in., Knudsen diffusion) to 10.0 {micro}m (3.9 x 10{sup -4} in., molecular diffusion). Predicted and measured oxidation rates were shown to have the same dependence upon porosity, pore radius, temperature, and oxygen partial pressure (P{sub O{sub 2}}). Use of the model was proposed for other oxidation systems and for chemical vapor infiltration (CVI). This work was part of the U.S. Bureau of Mines corrosion research program.
Date: July 1996
Creator: Holcomb, G. R.
Partner: UNT Libraries Government Documents Department

Surface and Electrochemical Behavior of HSLA in Supercritical CO2-H2O Environment

Description: General corrosion was observed on high strength low alloy carbon steel after electrochemical impedance spectroscopy experiments (EIS) performed in H{sub 2}O saturated with CO{sub 2} at 50 C and 15.2 MPa. However, general and localized were observed on the same material surfaces after the EIS experiments performed in supercritical CO{sub 2} containing approximately 6100 ppmv H{sub 2}O at 50 C and 15.2 MPa. The general corrosion areas were uniformly covered by the FeCO{sub 3}-like phase identified by X-ray diffraction (XRD). In the area of localized corrosion, XRD also revealed FeCO{sub 3}-rich islands embedded in {alpha}-iron. The energy dispersive X-ray (EDX) analysis revealed high concentrations of iron, carbon, and oxygen in the area affected by general corrosion and in the islands formed in the area of localized corrosion. The real and imaginary impedances were lower in H{sub 2}O saturated with CO{sub 2} than those in the supercritical CO{sub 2} containing the aqueous phase indicating faster corrosion kinetics in the former.
Date: January 11, 2012
Creator: Ziomek-Moroz, M.; Holcomb, G. R.; Tylczak, J.; Beck, J.; Fedkin, M. & Lvov, S.
Partner: UNT Libraries Government Documents Department

Task 2—Materials for Advanced Boiler and Oxy-combustion Systems (NETL-US),” a

Description: Develop a method for determining the solubility of protective oxides (Fe2O3, Cr2O3 and NiO) in an ash exposed at a particular temperature and gas composition. Metal oxide powder (Cr2O3 and NiO) will be mixed with a synthetic ash, milled for complete mixing, exposed at a variety of exposure times, and removed for analysis. • A decision will be made based on the results on to going further with the next tasks. • Perform the solubility tests on synthetic ashes and ashes collected from various oxyfuel burner rigs. • Correlate the solubility with long term corrosion tests and variables from the b i 4 burner rig tests.
Date: May 1, 2010
Creator: Holcomb, G. R.
Partner: UNT Libraries Government Documents Department

Quantitative X-ray microanalysis of submicron carbide formation in chromium (III) oxide rich scale

Description: This paper discusses the chemical microanalysis techniques adapted to identify the precipitates that form on the surface of, or within, the oxide scale of a Fe-22Cr ferritic steel during exposure to a carbon-monoxide rich environment at 750C for 800 hours. Examination of oxidized test coupons revealed the presence of a fiber like structure at the surface, shown in figure 1. Other studies have reported that these structures are carbon precipitates.
Date: August 1, 2007
Creator: Collins, W.K.; Ziomek-Moroz, M.; Holcomb, G.R.; Danielson, P. & Hunt, A.H
Partner: UNT Libraries Government Documents Department

Oxidation of interconnect alloys in an electric field

Description: The effect of an electric field on the oxidation of interconnect alloys was examined with a representative array of materials: an iron-base ferritic chromia former (E-brite), an iron-base ferritic chromia former with Mn and La (Crofer 22APU), a nickel-base chromia former (IN-718), and a nickelbase chromia former with Mn and La (Haynes 230). Environmental variables include temperature and oxygen partial pressure. The resulting scales were examined to determine if applied electrical current induces changes in mechanism or scale growth kinetics.
Date: October 1, 2006
Creator: Holcomb, G.R.; Alman, D.E.; Adler, T.A. & Jablonski, P.D.
Partner: UNT Libraries Government Documents Department

Influence of a Cerium Surface Treatment on the Oxidation Behavior of Cr2O3-Forming Alloys (title on slides varies: Oxidation Behavior of Cerium Surface Treated Chromia Forming Alloys)

Description: Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This temperature will require the construction of boiler and turbine components from austenitic stainless steels and nickel alloys. Many of the alloys being considered for use are primarily Cr2O3 forming alloys [1-4]. It is well known that the addition of a small amount of reactive elements, such as the rare earths elements Ce, La, and Y, can significantly improve the high temperature oxidation resistance of both iron- and nickel- base alloys. A list of the benefits of the reactive element effect include: (i) slowing scale growth, (ii) enhancing scale adhesion; and (iii) stabilizing Cr2O3 formation at lower Cr levels. The incorporation of the reactive element can be made in the melt or through a surface infusion or surface coating. Surface modifications allow for the concentration of the reactive element at the surface where it can provide the most benefit. This paper will detail a Ce surface treatment developed at NETL that improves the high temperature oxidation resistance of Cr2O3 forming alloys. The treatment consists of painting, dip coating, or spraying the alloy surface with a slurry containing CeO2 and a halide activator followed by a thermal treatment in a mild (x10-3 Torr) vacuum. During treatment the CeO2 reacts with the alloy to for a thin CrCeO3-type scale on the alloy surface. Upon subsequent oxidation, scale growth occurs at a reduced rate on alloys in the surface treated condition compared to those in the untreated condition.
Date: April 1, 2007
Creator: Alman, D.E.; Holcomb, G.R.; Adler, T.A. & Jablonski, P.D.
Partner: UNT Libraries Government Documents Department

Evaluation of a Surface Treatment on the Performance of Stainless Steels for SOFC Interconnect Applications

Description: Pack cementation-like Cerium based surface treatments have been found to be effective in enhancing the oxidation resistance of ferritic steels (Crofer 22APU) for solid oxide fuel cell (SOFC) applications. The application of either a CeN- or CeO2 based surface treatment results in a decrease in weight gain by a factor of three after 4000 hours exposure to air+3%H2O at 800oC. Similar oxide scales formed on treated and untreated surfaces, with a continuous Cr-Mn outer oxide layer and a continuous inner Cr2O3 layer formed on the surface. However, the thickness of the scales, and the amount of internal oxidation were significantly reduced with the treatment, leading to the decrease in oxidation rate. This presentation will detail the influence of the treatment on the electrical properties of the interconnect. Half-cell experiments (LSM cathode sandwiched between two steel interconnects) and full SOFC button cell experiments were run with treated and untreated interconnects. Preliminary results indicate the Ce treatment can improve SOFC performance.
Date: April 1, 2007
Creator: Alman, D. E.; Holcomb, G. R.; Adler, T. A.; Wilson, R. W. & Jablonski, P. D.
Partner: UNT Libraries Government Documents Department

Materials Performance in USC Steam

Description: The proposed steam inlet temperature in the Advanced Ultra Supercritical (A-USC) steam turbine is high enough (760 °C) that traditional turbine casing and valve body materials such as ferritic/martensitic steels will not suffice due to temperature limitations of this class of materials. Cast versions of several traditionally wrought Ni-based superalloys were evaluated for use as casing or valve components for the next generation of industrial steam turbines. The full size castings are substantial: 2-5,000 kg each half and on the order of 100 cm thick. Experimental castings were quite a bit smaller, but section size was retained and cooling rate controlled to produce equivalent microstructures. A multi-step homogenization heat treatment was developed to better deploy the alloy constituents. The most successful of these cast alloys in terms of creep strength (Haynes 263, Haynes 282, and Nimonic 105) were subsequently evaluated by characterizing their microstructure as well as their steam oxidation resistance (at 760 and 800 °C).
Date: May 1, 2010
Creator: Holcomb, G. R.; Wang, P.; Jablonski, P. D. & Hawk, J. A.
Partner: UNT Libraries Government Documents Department