By a News Reporter-Staff News Editor at Journal of Technology -- New research on Coatings Technology is the subject of a report. According to news originating from Maharashtra, India, by VerticalNews correspondents, research stated, "Ni-based superalloy 690 substrates were pack aluminized in a low Al-containing pack at 1273 K for 4 h in argon atmosphere. Scanning electron microscopy with energy dispersive X-ray analysis along the cross section of aluminized specimen revealed the formation of multilayer."
Our news journalists obtained a quote from the research from Bhabha Atomic Research Center, "The uppermost layer consisted of NiAl type phase (similar to 45 mu m), while adjoining one composed of (NiCr)Al and (NiCr)(2)Al types layer (similar to 25 mu m) and subsequently Cr-rich layer (similar to 35 mu m) adjacent to substrate. Al-content was found to increase while moving from Cr-rich layer towards outer layer. Cross-sectional transmission electron microscopy confirmed the formation of NiAl layer on the topmost surface and revealed the formation of nanoparticles of nickel aluminide on the uppermost surface. Microhardness was found to vary from 624 to 157 Vickers hardness number along the cross section of aluminized substrate indicating high, intermediate and low values for NiAl, Cr-rich layer and substrate, respectively. To evaluate the adherence of multilayer, scratch test was performed along the cross section of aluminized substrate at a constant load level of 2 N at ambient temperature. For aluminides, a decrease in friction coefficient with the decrease in Al-content was noticed. Cr-rich layer showed lowest friction coefficient, while its variation was little for substrate. Aluminide layers indicated lower penetration depth than the substrate, whereas no penetration was recorded for Cr-rich layer. Scratched surface did not reveal any peeling off either at the multilayer or layer/substrate interface indicating their good adherence. Aluminized specimens showed good overall oxidation resistance at 1273 K in air due to the formation of alpha-Al2O3."
According to the news editors, the research concluded: "First-principle spin-polarized calculations on Ni(111)/NiAl(110) interface indicated strong adhesion (Ideal work of adhesion, W-ad (ideal) = 3684 mj/m(2); lowest bound value) arising from strong metallic Ni d Ni d interaction and covalent Ni d Al p mixing of states."
For more information on this research see: Formation of aluminides on Ni-based superalloy 690 substrate, their characterization and first-principle Ni(111)/NiAl(110) interface simulations. Surface & Coatings Technology, 2013;235():741-747. Surface & Coatings Technology can be contacted at: Elsevier Science Sa, PO Box 564, 1001 Lausanne, Switzerland. (Elsevier - www.elsevier.com; Surface & Coatings Technology - www.elsevier.com/wps/product/cws_home/504101)
The news correspondents report that additional information may be obtained from R.S. Dutta, Bhabha Atom Res Center, Div Mat Sci, Bombay 400085, Maharashtra, India. Additional authors for this research include A. Arya, C. Yusufali, B. Vishwanadh, R. Tewari and G.K. Dey.
Keywords for this news article include: Asia, India, Maharashtra, Coatings Technology
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