Download or read book A Fundamental Study of Hot Corrosion and Interdiffusion of Chromium Aluminum and Silicon Coatings on a Nickel 201 Substrate written by Zachery Edward Gill and published by . This book was released on 2014 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern turbine engine systems require increased efficiency and durability. To achieve these goals, high-temperature materials with high-strength, low-cost and non-strategic compositions are needed. In advanced turbine applications, combustor liners, blades and vanes are exposed to corrosive combustion byproducts, such as alkali salts, at temperatures up to ~1700°C with high gas velocities, entrained particulates, and other foreign objects at pressures of up to 3 MPa (30 atm). These extreme conditions can drive a dangerous phenomenon known as "hot corrosion", an accelerated form of oxidation that occurs when metals and metal alloys are heated in the temperature range 700-900°C in the presence of alkali salts. An increased understanding of the fundamental behaviors of common high temperature alloys and their degradation mechanisms is therefore critical for the production of reliable components. In this study a model substrate, Nickel 201, was coated on one side with Cr, Al, or Si thin films (~1 micron) via magnetron sputtering physical vapor deposition (PVD). Uncoated and PVD coated samples were then exposed to laboratory air at 700°C and 900°C and to an environment similar in composition to atmospheres found in post combustion turbine systems, comprised of air/SO 2 gas mixture, at 700°C. The exposures were conducted over time intervals observing coating-substrate interactions and surface oxide development. Identical samples were subjected to the same exposures with addition of a deposit of sodium sulfate (Na 2SO 4), a model alkali salt. Sample mass gains were recorded and resulting oxide compositions assessed as a function of exposure time using microscopy techniques on sample surfaces and cross sections. The development of intermetallic species was determined by X-ray diffraction. At 700°C, coated and uncoated samples displayed different oxidation behaviors. Under laboratory air, no hot-corrosion occurred. While at 700°C in air/SO 2 exposures, evidence for hot corrosion on deposited samples was observed. When sodium sulfate was introduced at 900°C, coated and uncoated samples displayed rapid corrosion consistent with hot corrosion. The oxidation processes and coating/substrate inter-diffusion phenomena are presented and discussed in the context of establishing basic approaches to improve the fundamental understanding of hot corrosion, and the protection mechanisms of high temperature materials.

Download or read book Oxidation behaviour of MCrAlX coatings written by Pimin Zhang and published by Linköping University Electronic Press. This book was released on 2018-02-12 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt: MCrAlY coatings (M=Ni and/or Co) have been widely used for the protection of superalloy components against oxidation and hot corrosion in the hot sections of gas turbines. The drive to improve engine combustion efficiency while reducing emissions by increasing the operation temperature brings a big challenge for coating design. As a result, the need for improvement of MCrAlY coatings for better oxidation resistance is essential. Formation of a stable, dense, continuous, and slow-growing ?-Al2O3 layer, on the MCrAlY coating surface, is the key to oxidation protection, since the protective ?-Al2O3 scale offers superior oxidation resistance due to its lower oxygen-diffusion rate as compared with other oxides. The ability of a MCrAlY coating to form and maintain such a protective scale depends on the coating composition and microstructure, and can be improved through optimization of deposition parameters, modification of coating surface conditions, and so on. Part of this thesis work focuses on studying the effect of post-deposition surface treatments on the oxidation behavior of MCrAlX coatings (X can be yttrium and/or other minor alloying elements). The aim is to gain fundamental understanding of alumina scale evolution during oxidation which is important for achieving improved oxidation resistance of MCrAlX coatings. Oxide scale formed on coatings at initial oxidation stage and the effect of surface treatment were investigated by a multi-approach study combining photo-stimulated luminescence, microstructural observation and weight gain. Results showed that both mechanically polished and shot-peened coatings exhibited superior performance due to rapid formation of ?-Al2O3 fully covering the coating and suppressing growth of transient alumina, assisted by the high density of ?-Al2O3 nuclei on surface treatment induced defects. The early development of a two-layer alumina scale, consisting of an inward-grown inner ?-Al2O3 layer and an outer layer transformed from outward-grown transient alumina, resulted in a higher oxide growth rate of the as-sprayed coating. The positive effect of the surface treatments on retarding oxide scale growth and suppressing formation of spinel was also observed in oxidation test up to 1000 hrs. As the oxidation proceeds to the close-to-end stage, a reliable criterion to estimate the capability of coating to form ?-Al2O3 is of great importance to accurately evaluate coating lifetime, which is the aim of the other part of the thesis work. Survey of published results on a number of binary Ni-Al and ternary Ni-Cr-Al, Ni-Al-Si systems shows that the empirical Al-concentration based criterion is inadequate to properly predict the formation of a continuous ?-Al2O3 scale. On the other hand, correlating the corresponding Al-activity data, calculated from measured chemical compositions using the Thermo-Calc software, to the experimental oxidation results has revealed a temperature dependent, critical Al-activity value for forming continuous ?-Al2O3 scale. To validate the criterion, long-term oxidation tests were performed on five MCrAlX coatings with varying compositions and the implementation of the Al-activity based criterion on these coatings successfully predicted ?-Al2O3 formation, showing a good agreement with experiment results.

Download or read book Development of Binary and Ternary Chromium Aluminum Carbon Thin Film Coatings for Hot Corrosion Prevention written by Lik Ming Aw and published by . This book was released on 2015 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing the operating temperature of high temperature energy conversion systems is often very desirable in order to maximize their corresponding efficiencies. Materials selected for high temperature applications must therefore incorporate associated considerations such as creep strength, high temperature corrosion resistance, and thermal fatigue. Hot corrosion is a form of accelerated high temperature oxidation associated with the deposition of salt such as sodium sulfate (Na 2SO 4) on metals or their protective oxide surfaces. Severe corrosion develops when Na 2SO 4 reacts with metals to form eutectic (low-melting point) compositions on the surface of the metal at 700 °C (Type II Hot Corrosion) or when the surface has been wetted by molten Na 2SO 4 at 900 °C (Type I Hot Corrosion). This phenomenon reduces the useful life of materials such as nickel alloys used in high temperature gas turbines for aircraft and marine applications. In this study, a variety of binary and ternary thin film coatings using chromium, aluminum, and carbon as base elements were deposited onto Ni-201 alloy and investigated as a function of exposure to hot corrosion environments. The coatings were deposited using a magnetron sputtering system and were approximately 1.5 microns in thickness. Prototypical Na 2SO 4 was applied to the samples before exposing them for up to 250 hours in an air/SO 2 gas mixture at 700 °C and 900 °C, which simulates Type II and Type I Hot Corrosion, respectively. It was determined that all coatings reduced the specific mass gains (corrosion rates) of the samples when compared to that of an uncoated sample, indicating that they provided protection against hot corrosion. For Type II Hot Corrosion, binary Cr - Al and ternary Cr - Al - C thin film coatings held up after 250 hours of exposure; whereas the other two coatings had completely disintegrated. For Type I Hot Corrosion, all thin film coatings utilized in the study had completely dissolved after 50 hours of exposure. It was suggested that the two most effective coating materials, Cr -Al and Cr - Al - C coatings should be used for future testing and that their thicknesses should be increased to help provide better protection against Type I Hot Corrosion.

Download or read book Exploratory Study of Silicide Aluminide and Boride Coatings for Nitridation oxidation Protection of Chromium Alloys written by Joseph R. Stephens and published by . This book was released on 1969 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chromium alloys were coated with silicon, aluminum, and boron by pack cementation. None of these simple coatings provided adequate nitridation-oxidation protection for a chromium +0.17 wt % yttrium alloy substrate as shown by a substantial increase in the ductile-brittle transition temperature after air exposure for 100 hr at 2100 degrees F (1420 K). Iron modified silicides coatings afforded good protection, holding the transition temperature of air exposed specimens to 3500 F (450 K) compared to 200 degrees F (370 K) for recrystallized uncoated specimens. Additional attractive modifying elements included iron-molybdenum, iron-molybdenum-tungsten, iron-molybdenum-tungsten-titanium and vanadium-molybdenum-tungsten-titantum.

Download or read book Materials and Coatings to Resist High Temperature Corrosion written by Derek Roy Holmes and published by . This book was released on 1978 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tailored Thin Coatings for Corrosion Inhibition Using a Molecular Approach written by Simo Olavi Pehkonen and published by Academic Press. This book was released on 2018-08-25 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tailored Thin Coatings for Corrosion Inhibition Using a Molecular Approach discusses the fundamentals and applications of various thin coatings for the inhibition of fouling and corrosion from a molecular perspective. It provides the reader with a fundamental understanding of why certain coatings perform better than others in a given environment. Surface analytical and electrochemical techniques in understanding the coating performance are emphasized throughout the book, providing readers with a useful reference on how to pursue a systematic corrosion inhibitor R&D program that involves the testing of coating performance using various, currently available, state-of-the-art laboratory techniques. Wherever relevant, environmental considerations of the discussed coatings’ technologies are highlighted and discussed, with current and upcoming regulatory trends put forth by different governmental organizations. Provides atomic and molecular level understanding of tailored thin coatings for corrosion inhibition Discusses key steps in corrosion, including the attachment of harmful substances to surfaces, the fouling of surfaces, and the initiation and propagation of corrosion on surfaces Written by leading experts in the field

Download or read book Hot Corrosion of the B2 Nickel Aluminides written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-25 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hot corrosion behavior of the B2 nickel aluminides was studied to determine the inherent hot corrosion resistance of the beta nickel aluminides and to develop a mechanism for the hot corrosion of the beta nickel aluminides. The effects of the prior processing of the material, small additions of zirconium, stoichiometry of the materials, and preoxidation of the samples were also examined. Additions of 2, 5, and 15 w/o chromium were used to determine the effect of chromium on the hot corrosion of the beta nickel aluminides and the minimum amount of chromium necessary for good hot corrosion resistance. The results indicate that the beta nickel aluminides have inferior inherent hot corrosion resistance despite their excellent oxidation resistance. Prior processing and zirconium additions had no discernible effect on the hot corrosion resistance of the alloys. Preoxidation extended the incubation period of the alloys only a few hours and was not considered to be an effective means of stopping hot corrosion. Stoichiometry was a major factor in determining the hot corrosion resistance of the alloys with the higher aluminum alloys having a definitely superior hot corrosion resistance. The addition of chromium to the alloys stopped the hot corrosion attack in the alloys tested. From a variety of experimental results, a complex hot corrosion mechanism was proposed. During the early stages of the hot corrosion of these alloys the corrosion is dominated by a local sulphidation/oxidation form of attack. During the intermediate stages of the hot corrosion, the aluminum depletion at the surface leads to a change in the oxidation mechanism from a protective external alumina layer to a mixed nickel-aluminum spinel and nickel oxide that can occur both externally and internally. The material undergoes extensive cracking during the later portions of the hot corrosion. Ellis, David L. Unspecified Center NASA-CR-191082, E-7621, NAS 1.26:191082 NCC3-94; RTOP 505-63-40...

Download or read book High Temperature Coatings written by Sudhangshu Bose and published by Elsevier. This book was released on 2011-04-01 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: High Temperature Coatings demonstrates how to counteract the thermal effects of the rapid corrosion and degradation of exposed materials and equipment that can occur under high operating temperatures. This is the first true practical guide on the use of thermally-protective coatings for high-temperature applications, including the latest developments in materials used for protective coatings. It covers the make-up and behavior of such materials under thermal stress and the methods used for applying them to specific types of substrates, as well as invaluable advice on inspection and repair of existing thermal coatings.With his long experience in the aerospace gas turbine industry, the author has compiled the very latest in coating materials and coating technologies, as well as hard-to-find guidance on maintaining and repairing thermal coatings, including appropriate inspection protocols. The book will be supplemented with the latest reference information and additional support for finding more application-type and industry-type coatings specifications and uses, with help for the reader in finding more detailed information on a specific type of coating or a specific type of use.· Offers overview of the underlying fundamental concepts of thermally-protective coatings, including thermodynamics, energy kinetics, crystallography, and equilibrium phases· Covers essential chemistry and physics of underlying substrates, including steels, nickel-iron alloys, nickel-cobalt alloys, and titanium alloys· Provides detailed guidance on wide variety of coating types, including those used against high temperature corrosion and oxidative degradation, as well as thermal barrier coatings

Download or read book High temperature Oxidation resistant Coatings written by National Research Council (U.S.). Committee on Coatings and published by National Academies. This book was released on 1970 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Experimental Low cost Silicon Slurry aluminide High temperature Coating for Superalloys written by and published by . This book was released on 1979 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Metallurgical and Ceramic Protective Coatings written by K.H. Stern and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 353 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface engineering is an increasingly important field and consequently those involved need to be aware of the vast range of technologies available to modify surfaces. This text provides an up-to-date, authoritative exposition of the major condensed phase methods used for producing metallurgical and ceramic coatings. Each method is discussed thoroughly by an expert in that field. In each chapter the principle of the method, its range of applications and technical aspects involved are described. The book not only informs the reader about established technologies familiar only to specialists, but also details activity on the frontier of coating technology providing an insight into those potential technologies not yet fully developed but which should emerge in the near future.

Download or read book Reaction Diffusion in the Nickel chromium aluminum and Cobalt chromium aluminum Systems written by Stanley R. Levine and published by . This book was released on 1977 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Diffusion and High Temperature Oxidation of Nickel aluminum Based Composite Coatings written by Donald F. Susan and published by . This book was released on 1999 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt: The diffusion and oxidation behavior of electrodeposited composite coatings were studied using thermogravimetric analysis, electron probe microanalysis, and microstructural characterization techniques. Deposition of Al and Al-Si particles into a Ni matrix produced binary and ternary composite coatings with a uniform particle distribution. During heat treatment, coating morphological development was found to occur by the exothermic reaction Ni + Al & rarr; NiAl followed by interdiffusion to form a final gamma + gamma' microstructure. During oxidation at 800°C, the gamma + gamma ' coatings formed a gamma-A12O3 layer below an outer NiO scale. At 1000°C, theta-Al2O3 needles are formed in the early stages. At later times, an alpha-Al2O3 layer is found below an outer spinel NiAl2O4 scale. At both temperatures, the Al2O3 layer provides good oxidation resistance during long-term exposure. The coatings were compared to bulk Ni-Al alloys, and a critical Al content of about 6 wt. % was found, below which internal oxidation attack may occur. During exposure at high temperatures, interdiffusion occurs between the Ni-Al coating and the Ni substrate. The diffusion process was modeled using an analytical solution to Fick's second law. The Al content at the coating surface was monitored using EPMA and the results were in agreement with the predicted values from the diffusion equation. Estimates of coating lifetime were made by combining the diffusion results with knowledge of the effect of Al content on oxidation behavior. The results showed that practical use temperatures for Ni-Al coatings are 700--800°C. At 1000--1100°C, Al depletion begins after a few hundred hours and predicted coating lifetimes are in the range of a few thousand hours.

Download or read book A Study of Alumosiliconized Diffusion Layers on Nickel Chromium Alloy written by G. V. Zemskov and published by . This book was released on 1970 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the study of alumosiliconized coatings, the following differences from calorized coatings were observed: (1) the presence of 5-7% Si; (2) increased aluminum content and a correspondingly decreased nickel content; (3) a reduction in the number of other phases, besides the phase on a Ni2Al3 base. All the indicated differences contribute to the heightened oxidation resistance of the complex diffusion layer. (Author).

Download or read book An Investigation of the Hot Corrosion Protectivity Behavior of Platinum Modified Aluminide Coatings on Nickel based Superalloys written by Rudolph E. Malush and published by . This book was released on 1987 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of Vanadium and Hot corrosion Resistance of Chromium and Silicon base Coating Systems written by R. H. Barkalow and published by . This book was released on 1983 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Chromium Addition to the Low Temperature Hot Corrosion Resistance of Platinum Modified Aluminide Coatings written by Mark W. Dust and published by . This book was released on 1985 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: Marine gas turbines face many adverse conditions such as reduced fuel quality and a salt environment which present the sulfur, chloride, and sulfates required to initiate and propagate hot corrosion. A particularly severe type of hot corrosion is low temperature hot corrosion (LTHC) encountered at the low temperatures (600-750 C) used for low power destroyer operations. Platinum-aluminides have demonstrated great success as protective coatings which delay the onset of high temperature hot corrosion attack (800-1000 C). Chromium is known to provide good LTHC resistance. The effect of chromium addition to platinum aluminide coatings was investigated using two different nickel base superalloys, IN-738 (16% Cr) and IN-100 (10% Cr). Keywords: Platinum Aluminide, Chromium Aluminide; Nickel base Superalloy; IN-738; In-100; Thesis.