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Pack cementation diffusion coatings for iron-base alloys

Description: With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels. The Cr-Si ferrite layers have proven to be very resistant to high temperature cyclic oxidation and to pitting in aqueous solutions. The process has been patented, and is being transferred for industrial application, e.g. for water walls of utility boilers, etc. In the proposed extension of this project, the use of mixed pure metal powders in the pack will be extended to achieve similar ferrite Fe-Cr-Al coatings with excellent oxidation resistance, with the eventual transfer of the technology to industry. In other recent studies, Ni-base alloy rods were aluminized by the halide-activated pack cementation process to bring their average composition to that for the ORNL-developed Ni{sub 3}Al, for use as a welding rod. A similar effort to develop a welding rod for the ORNL Fe{sub 3}Al alloy did not yield reproducible coating compositions or growth kinetics. The continued effort to produce Duriron-type (Fe-18Si-5Cr) coatings on steels was not successful. Literature for the intrinsic diffusion coefficients suggests that this task cannot be achieved.
Date: February 1, 1995
Creator: Rapp, R. A.
Partner: UNT Libraries Government Documents Department

Diffusion Coatings for Corrosion-Resistant Components in Coal Gasification Systems

Description: Heat-exchangers, particle filters, turbines, and other components in integrated coal gasification combined cycle system must withstand the highly sulfiding conditions of the high temperature coal gas over an extended period of time. The performance of components degrades significantly with time unless expensive high alloy materials are used. Deposition of a suitable coating on a low-cost alloy may improve its resistance to such sulfidation attack, and decrease capital and operating costs. The alloys used in the gasifier service include austenitic and ferritic stainless steels, nickel-chromium-iron alloys, and expensive nickel-cobalt alloys. The primary activity this period was preparation and presentation of the findings on this project at the Twenty-Third annual Pittsburgh Coal Conference. Dr. Malhotra attended this conference and presented a paper. A copy of his presentation constitutes this quarterly report.
Date: September 30, 2006
Creator: Krishnan, Gopala N.; Malhotra, Ripudaman; Alvarez, Esperanza; Lau, Kai-Hung; Mariano, Jordi Perez & Sanjurjo, Angel
Partner: UNT Libraries Government Documents Department

A Novel Low-Temperature Fiffusion Aluminide Coating for Ultrasupercritical Coal-Fried Boiler Applications

Description: An ultrasupercritical (USC) boiler with higher steam temperature and pressure is expected to increase the efficiency of the coal-fired power plant and also decrease emissions of air pollutants. Ferritic/martensitic alloys have been developed with good creep strength for the key components in coal-fired USC plants. However, they typically suffer excessive steam-side oxidation, which contributes to one of main degradation mechanisms along with the fire-side corrosion in coal-fired boilers. As the steam temperature further increases in USC boilers, oxidation of the tube internals becomes an increasing concern, and protective coatings such as aluminide-based diffusion coatings need to be considered. However, conventional aluminizing processes via pack cementation or chemical vapor deposition are typically carried out at elevated temperatures (1000-1150 C). Thermochemical treatment of ferritic/martensitic alloys at such high temperatures could severely degrade their mechanical properties, particularly the alloy's creep resistance. The research focus of this project was to develop an aluminide coating with good oxidation resistance at temperatures {le} 700 C so that the coating processing would not detrimentally alter the creep performance of the ferritic/martensitic alloys. Nevertheless, when the aluminizing temperature is lowered, brittle Al-rich intermetallic phases, such as Fe{sub 2}Al{sub 5} and FeAl{sub 3}, tend to form in the coating, which may reduce the resistance to fatigue cracking. Al-containing binary masteralloys were selected based on thermodynamic calculations to reduce the Al activity in the pack cementation process and thus to prevent the formation of brittle Al-rich intermetallic phases. Thermodynamic computations were carried out using commercial software HSC 5.0 for a series of packs containing various Cr-Al binary masteralloys. The calculation results indicate that the equilibrium partial pressures of Al halides at 700 C were a function of Al content in the Cr-Al alloys. Cr-25Al and Cr-15Al were chosen as the masteralloys in the pack cementation process. In contrast to pure ...
Date: December 31, 2009
Creator: Zhang, Ying
Partner: UNT Libraries Government Documents Department

DIFFUSION COATINGS FOR CORROSION RESISTANT COMPONENTS IN COAL GASIFICATION SYSTEMS

Description: Heat-exchangers, particle filters, turbines, and other components in integrated coal gasification combined cycle system must withstand the highly sulfiding conditions of the high temperature coal gas over an extended period of time. The performance of components degrades significantly with time unless expensive high alloy materials are used. Deposition of a suitable coating on a low cost alloy may improve is resistance to such sulfidation attack and decrease capital and operating costs. The alloys used in the gasifier service include austenitic and ferritic stainless steels, nickel-chromium-iron alloys, and expensive nickel-cobalt alloys. During this reporting period we coated coupons of selected alloy steels with diffusion coatings of Cr and Al, as well as with titanium and tantalum nitrides. The coated samples were analyzed for their surface composition. In several instances, the samples were also cut to determine the depth profile of the coating. Several of the early runs did not yield uniform or deep enough coatings and hence a significant portion of the effort in this period was devoted fixing the problems with our fluidized bed reactor. Before the end of the quarter we had prepared a number of samples, many of them in duplicates, and sent one set to Wabash River Energy Laboratory for them to install in their gasifier. The gasifier was undergoing a scheduled maintenance and thus presented an opportunity to place some of our coupons in the stream of an operating gasifier. The samples submitted included coated and uncoated pairs of different alloys.
Date: January 1, 2005
Creator: Krishnan, Gopala N.; Malhotra, Ripudaman; Alvarez, Esperanza; Lau, Kai-Hung & Sanjurjo, Angel
Partner: UNT Libraries Government Documents Department

DIFFUSION COATINGS FOR CORROSION RESISTANT COMPONENTS IN COAL GASIFICATION SYSTEMS

Description: Heat-exchangers, particle filters, turbines, and other components in integrated coal gasification combined cycle system must withstand the highly sulfiding conditions of the high temperature coal gas over an extended period of time. The performance of components degrades significantly with time unless expensive high alloy materials are used. Deposition of a suitable coating on a low cost alloy may improve is resistance to such sulfidation attack and decrease capital and operating costs. The alloys used in the gasifier service include austenitic and ferritic stainless steels, nickel-chromium-iron alloys, and expensive nickel-cobalt alloys. A review of the literature indicated that the Fe- and Ni-based high-temperature alloys are susceptible to sulfidation attack unless they are fortified with high levels of Cr, Al, and Si. To impart corrosion resistance, these elements need not be in the bulk of the alloy and need only be present at the surface layers. We selected diffusion coatings of Cr and Al, and surface coatings of Si and Ti for the preliminary testing. These coatings will be applied using the fluidized bed chemical vapor deposition technique developed at SRI which is rapid and relatively inexpensive. We have procured coupons of typical alloys used in a gasifier. These coupons will be coated with Cr, Al, Si, and Ti. The samples will be tested in a bench-scale reactor using simulated coal gas compositions. In addition, we will be sending coated samples for insertion in the gas stream of the coal gasifier.
Date: May 1, 2004
Creator: Krishnan, Gopala N.; Malhotra, Ripudaman & Sanjurjo, Angel
Partner: UNT Libraries Government Documents Department

Diffusion Coatings for Corrosion-Resistant Components in Coal Gasification Systems

Description: Heat-exchangers, particle filters, turbines, and other components in integrated coal gasification combined cycle system must withstand the highly sulfiding conditions of the hightemperature coal gas over an extended period of time. The performance of components degrades significantly with time unless expensive high alloy materials are used. Deposition of a suitable coating on a low-cost alloy may improve its resistance to such sulfidation attack, and decrease capital and operating costs. The alloys used in the gasifier service include austenitic and ferritic stainless steels, nickel-chromium-iron alloys, and expensive nickel-cobalt alloys. During this period, we analyzed several 409 low alloy steel samples after coating them in our fluidized bed reactor and also after exposing them to our corrosion test. We report the following findings: 1. A protective coating was deposited inside a porous 409 steel sample to protect it from sulfidation attack. The coating was based on a combination of Si diffusion layer, Nb interlayer and nitrides of titanium and silicon. 2. Analysis of solid coupons exposed to simulated coal gas at 900 C for 300 h showed that multilayer metal/ceramic coatings provide a better protection than ceramic coatings. 3. Deposition of several ceramic/metal multilayer coatings showed that coatings with niobium and tantalum interlayers have good adhesion. However, coatings with a tungsten interlayer suffered localized delaminating and coatings with Zr interlayers showed poor adhesion. 4. Analysis of solid coupons, coated with the above-mentioned multilayer films, after exposure to simulated coal gas at 900 C for 300 h showed that niobium is the best candidate for interlayer material.
Date: March 31, 2007
Creator: Krishnan, Gopala N.; Malhotra, Ripudaman; Alvarez, Esperanza; Lau, Kai-Hung; Perez-Mariano, Jordi & Sanjurjo, Angel
Partner: UNT Libraries Government Documents Department

Theory and simulations of Zone II microstructures in thin films

Description: The nature of the microstructure of vapor-deposited films is known to depend sensitively on the substrate temperature during deposition. At intermediate temperatures (T approx. .45 Tm where Tm is the melting point of the film) the film is made up of columnar-grains separated by metallurgical grain boundaries. Both an analytical and numerical analysis is presented in which the space-time evolution of the columnar microstructure (Zone II) is studied.
Date: January 1, 1987
Creator: Srolovitz, D.J.; Mazor, A.; Bukiet, B.G. & Hagan, P.S.
Partner: UNT Libraries Government Documents Department

Research on advanced photovoltaic manufacturing technology

Description: This report outlines opportunities for significantly advancing the scale and economy of high-volume manufacturing of high-efficiency photovoltaic (PV) modules. We propose to pursue a concurrent effort to advance existing crystalline silicon module manufacturing technology and to implement thin film CuInSe{sub 2} (CIS) module manufacturing. This combination of commercial-scale manufacturing of high-efficiency crystalline silicon modules and of pilot-scale manufacturing of low-cost thin film CIS technology will support continued, rapid growth of the US PV industry.
Date: November 1, 1991
Creator: Jester, T. & Eberspacher, C. (Siemens Solar Industries, Camarillo, CA (United States))
Partner: UNT Libraries Government Documents Department

Diffusion Coatings for Corrosion-Resistant Components in Coal Gasification Systems

Description: Advanced electric power generation systems use a coal gasifier to convert coal to a gas rich in fuels such as H{sub 2} and CO. The gas stream contains impurities such as H{sub 2}S and HCl, which attack metal components of the coal gas train, causing plant downtime and increasing the cost of power generation. Corrosion-resistant coatings would improve plant availability and decrease maintenance costs, thus allowing the environmentally superior integrated-gasification-combined-cycle (IGCC) plants to be more competitive with standard power-generation technologies. Heat-exchangers, particle filters, turbines, and other components in the IGCC system must withstand the highly sulfiding conditions of the high-temperature coal gas over an extended period of time. The performance of components degrades significantly with time unless expensive high alloy materials are used. Deposition of a suitable coating on a low cost alloy will improve is resistance to such sulfidation attack and decrease capital and operating costs. The alloys used in the gasifier service include austenitic and ferritic stainless steels, nickel-chromium-iron alloys, and expensive nickel-cobalt alloys. The Fe- and Ni-based high-temperature alloys are susceptible to sulfidation attack unless they are fortified with high levels of Cr, Al, and Si. To impart corrosion resistance, these elements need not be in the bulk of the alloy and need only be present at the surface layers. In this study, the use of corrosion-resistant coatings on low alloy steels was investigated for use as high-temperature components in IGCC systems. The coatings were deposited using SRI's fluidized-bed reactor chemical vapor deposition technique. Diffusion coatings of Cr and Al were deposited by this method on to dense and porous, low alloy stainless steel substrates. Bench-scale exposure tests at 900 C with a simulated coal gas stream containing 1.7% H{sub 2}S showed that the low alloy steels such SS405 and SS409 coated with {approx}20%Cr and Al each ...
Date: May 31, 2007
Creator: Krishnan, Gopala N.; Malhotra, Ripudaman; Perez, Jordi; Hornbostel, Marc; Lau, Kai-Hung & Sanjurjo, Angel
Partner: UNT Libraries Government Documents Department

Phase 2, automated array assembly, Task IV, low-cost silicon solar array project. Quarterly report No. 3

Description: Functional 3-inch diameter reference cells were fabricated using conventional processes consisting of: POCL/sub 3/ diffusion, electroless nickel plating, solder dipping, and evaporated SiO AR coating. Both flash and texture-etched surface wafers were used. The flash-etched cells yielded output efficiencies of 10.3%, whereas the texture-etched cells were considerably lower. Other flash and texture-etched cells were processed by /sup 31/P ion implantation 25 keV and 3 x 10/sup 15/ ions/cm/sup 2/, thermal annealing, and electroless nickel plating, resulting in 7% AM1 efficiencies. Problems were experienced in the nickel plating process which contributed to poor ohmic contact adherence and the resulting low efficiencies. Laser annealing was performed by Quantronix with an Nd:YAG laser on our texture-etched, flash-etched, and polished ion implanted wafers. A programmed X-Y positioning stage was used for precise traversing across the wafer surface. Best results of 7.3% AM1 efficiencies were attained on .5 x .5 cm size cells with polished surfaces. These cells had evaporated Ti/Ag contacts but not sintered nor AR coated. I/sub sc/ of these small cells was 5 ma. This represents a 27 ma/cm/sup 2/ output based on active area only, and compares with 32 ma/cm/sup 2/ for a conventionally processed cell of 11% AM1 efficiency. A cost analysis was prepared which reflects potential cost savings of laser annealing over thermal annealing in excess of $35 million. This savings is due to a projected cell efficiency improvement of 2%, resulting in reduced quantities of cells for the 500 megawatt capability. Spraying of tantalum solutions was performed on 2 x 4 cm space cells using the Zicon Autocoater. Cells were electrically tested at the outset in the as-received condition with SiO AR coating.
Date: July 1, 1978
Partner: UNT Libraries Government Documents Department

Effect of S8DR chromium diffusion treatment on the creep rupture properties of processed Hastelloy-N tubing

Description: Process development personnel have been seeking means of improving the (after thermal exposure) adhesion of the S8DR ceramic coating to chromized Hastelloy N tubing. This effort has led to the incorporation of an elevated temperature chromium diffusion treatment prior to the application of the ceramic coating. This report describes the results of tests performed to ascertain the influence of the additional thermal treatment on the 1400/sup 0/F creep-rupture properties of S8DR tubing.
Date: June 3, 1967
Creator: Allaria, G.G.
Partner: UNT Libraries Government Documents Department