Selected Abstracts of Thermal Spray Literature
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Selected Abstracts of Thermal Spray Literature Reprinted with permission from Elsevier Engineering Information, Inc., Hoboken, NJ
Applications Aerospace Blade failure in second stage turbine. The present paper reports the investigation of a sudden blade fracture leading to a fatal engine failure. The blade sample was subjected to a series of examinations, including visual examination and photographic documentation, optical microscopy, scanning electron microscopy (SEM), using both energy dispersive spectroscopy (EDS) and x-ray mapping. Analysis of all elements show that loss of aluminum from coating due to oxidation and coating phases changing; decreasing of alloy ductility and toughness due to carbides precipitation in grain boundaries; degradation of the alloy d0 & d1 phase (aging and coarsening) and micro cavities. These were found on fracture surfaces which served as an origin of creeping failure mechanism and are the most important factor for failure of this blade. K. Mohammadi and A.K. Haghi, University of Guilan, Rasht, Iran. Cited: Key Eng. Mater., p 393-396. ISSN 1013-9826. Characterization of HVOF sprayed NiCrAlY-0-4wt.%CeO2 coatings on superalloys. In the present work, metallurgical and mechanical properties of high velocity oxy fuel thermal sprayed NICrAlY-0-4wt.%CeO2 coatings on NI and Fe based superalloys have been investigated. The microstructural morphologies, composition, and phases of the coatings were characterised using the techniques such as optical microscopy, field emission scanning electron microscopy/energy dispersive spectroscopy and x-ray diffraction. The mechanical properties of coatings such as microhardness and adhesion strength were measured. The coatings exhibited characteristic splat like, layered morphologies due to the deposition and resolidification of successive molten or semimolten powder particles. The coatings contained less than 1-4% porosity and showed the measured hardness values in the range of 649753 HV. Average bond strength of the coating was found to be 45 MPa. The observed higher values of microhardness of the coated samples might be attributed to the addition of small amount of rare earth oxide CeO2 in the coatings. R.A. Mahesh, R. Jayaganthan, and S. Prakash, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee 247667, India. Cited: Surf. Eng., 2008, Sept, 24(5), p 366-373. ISSN 02670844. Hard chromium substitution using HVOF coatings. Electroplated hard chromium coatings have long been used to improve the wear and/or corrosion resistance of components. However, concerns over the health problems associated with hexavalent chromium solutions have led to increasing regulation of this process route. One promising substitute for hard chromium is ÔcermetÕ layers (e.g. Cr3C2-NiCr and WC-CoCr) which may be deposited by the high velocity oxyfuel process. High velocity oxyfuel coatings were characterized by microscopy, x-ray spectroscopy, density and a microabrasive wear test. The WC-CoCr coating provided the best overall per
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