ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Spherical Al particles sized in the range of 2 to 5 μm were deposited with an organicbinder by brushing on the austenitic steel X6 CrNi 18-10 (Alloy 304H). The coated samples wereannealed in air at 400°C for 1 h in order to expel the binder. For studying the oxidation behaviour inair, isothermal experiments were performed at 700°C and 900°C with oxidation times of 5 h, 100 hand 1000 h. The oxide formation was studied in situ by high temperature X-ray diffraction (HTXRD)up to 100 h. Field emission scanning electron microscopy (FE-SEM) was applied to investigatethe surface and the cross-section of the particle coating.During oxidation, the stable α-Al2O3 was identified in situ by HT-XRD on all studied samples atboth temperatures. No meta-stable alumina phases were found. In the initial state, 2 h at 900°C, theAl particles are completely oxidised to hollow alumina spheres, controlled predominantly by thereaction due to the small particle size and relatively high surface portion. Simultaneously, the Alrichdiffusion layer is formed in the substrate. On further exposure, a thin protective alumina scalecontinues growing on the top of the diffusion layer. After exposure to both 700°C and 900°C, acoating structure was encountered, which consists of a quasi-foam top coat from conjoint hollowspherical alumina particles and an Al-rich diffusion layer below. The quasi-foam top coat has thepotential to effectuate as thermal barrier by gas phase insulation, while the diffusion layer belowserves as protective coating against oxidation.The approach by particle size processing opens a potential for obtaining a complete thermal barriercoating system in one manufacturing step. The coating properties can be adjusted by parameterslike selection of source metal/alloy, particle size, substrate, binder and heat treatment
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/19/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.595-598.769.pdf
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