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The Hot Corrosion Resistance of Platinum–Rhodium Modified Diffusion Coating on Directionally Solidified MAR M002 Superalloy at 900°C
Published in J. Nicholls, D. Rickerby, High Temperature Surface Engineering, 2020
W. Y. Chan, P. K. Datta, G. Fisher, J. S. Burnell-Gray
The development of new aluminide coatings is a continuing process, motivated primarily by the demand for materials with enhanced oxidation and hot corrosion resistance, and high temperature stability for use in modern gas turbine engines. Aluminide coatings developed by the pack-cementation process have been used extensively against hot corrosion of nickel and cobalt superalloys in gas turbine application.1–3 Corrosion of material in the presence of liquid sodium sulphate, either by itself or in combination with sodium chloride, has been a problem in gas turbines; this corrosion process has been termed ‘hot corrosion’ which is often described as an accelerated form of corrosion in the presence of oxygen and sulphur.4 Two types of hot corrosion have been identified: Type I, high temperature hot corrosion (HTHC), operative at 800–950°C or higher, and Type II, low temperature hot corrosion (LTHC), operative at 600–750°C.
Synthesis and Characterization of Copper–Ruthenium Composites
Published in Ajay Kumar Mishra, Lallan Mishra, Ruthenium Chemistry, 2018
Rasidi Sule, Iakovos Sigalas, Joseph Kwaku Ofori Asante, Peter Apata Olubambi
Nickel and titanium aluminide systems have been widely used for high-temperature structural applications due their strength, high oxidation and corrosion resistance, and high melting point (Bora et al., 2004). The application of these alloy systems at high temperature is limited by their poor room temperature ductility and fracture toughness (Bora et al., 2004). In order to overcome these challenges, a material with high strength at room and elevated temperatures as well as room temperature ductility and toughness could be incorporated.
CVD coatings
Published in Kwang Leong Choy, Chemical Vapour Deposition (CVD), 2019
Aluminising is a commonly used industrial processes for producing diffusion bond coats (e.g., aluminides) by aluminising the outer surface of aero and industrial turbine blades. This helps not only to improve adhesion of the ceramic top coat to the Ni-superalloy substrate by minimising their thermal expansion mismatch but also to provide the desired resistance to high-temperature oxidation and corrosion in extreme environments.
EUROCORR 2019: ‘New Times, New Materials, New Corrosion Challenges’ – Part 3
Published in Corrosion Engineering, Science and Technology, 2020
F. Pedraza (Université de La Rochelle, France) discussed ‘Degradation of unmodified and Si-modified aluminide coatings in Type II hot corrosion conditions’. Si-modified aluminide coatings are widely employed for the hottest sections of aeronautic turbines against hot corrosion. Al/Si slurries to fabricate the coatings often contain chromates (carcinogenic); so replacement Cr (VI)-free water-based slurries have been explored. The mechanism of the formation of the Si-modified aluminide coatings on pure nickel, and their hot corrosion mechanisms at 700°C for up to 300 h, were investigated. The influence of the test method (salt embedment vs. salt spray) with Na2SO4 and of the atmosphere (air vs. 0.5% SO2/SO3) was discussed. The oxide scale on the Al/Si was so thin under all conditions as to be undetectable by SEM/EDS, Raman spectroscopy or XRD. Neither degradation nor pitting was found on the heat-affected surfaces. In contrast, the simple aluminide coating developed some pits associated with inadequate formation of the protective alumina scales.
Aluminising of steel with a cathodic arc plasma based method
Published in Transactions of the IMF, 2019
T. Çelikel, E. Kacar, M. Ürgen
Iron aluminide coatings are produced by diffusion processes between the iron-based substrates and Al that is deposited on them. They are generally used for improving high-temperature oxidation and corrosion resistance of steel components.1–3 Aluminide coatings form stable and protective oxides, and they have excellent resistance to gaseous environments containing sulphur compounds.4,5 Therefore, aluminised steel finds applications in coal gasification plants, petroleum refineries, petrochemical industry and coal using energy centres.6,7 Depending on the method of aluminising and process temperature, it is possible to produce coatings that are rich in aluminium or rich in iron. Iron-rich aluminide coatings are of interest due to their higher melting temperatures, toughness, mechanical properties and also the possibility of producing them in ordered structures.8
On the formation of temperature-induced defects at the surface of TEM specimens prepared from TiAl using high-energy Gallium and low-energy Argon ions
Published in Philosophical Magazine, 2020
Two-phase γ titanium aluminides are used in some high-temperature aero-engine applications because of their low density and high structural stability. Of particular interest are the so-called high Nb-containing alloys within the base-composition range Ti-(44-47)Al-(5-8)Nb (in at %) [4,5] standing out due to high attainable strengths and sufficient ductilities. The alloys mainly consist of the intermetallic phases γ(TiAl) with L10 structure and α2(Ti3Al) with D019 structure, where the volume fraction of the α2 phase is between 5 and 20%. The atomic arrangements of the phases are depicted in Figure 1 together with the Burgers vectors of the γ phase.