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Minneapolis, MN, United States

Wang Y.,SIFCO Minneapolis
Surface and Coatings Technology | Year: 2011

Hf-modified and Hf-Pt-modified aluminide coatings on Haynes 188 Co-base alloy coupons were developed and furthermore, Hf-modified aluminide coatings on MAR-M-509 Co-base aircraft turbine engine vane segments were produced for potential industrial applications. Surface morphology and cross-section microstructure of the developed coatings were inspected and compared by using Scanning Electron Microscope (SEM) equipped with energy dispersive spectroscopy (EDS), and Glow-Discharge Mass Spectrometry (GDMS). Experimental results showed that Hf was successfully incorporated and localized Hf-rich precipitated phase particles were observed on the coating surface and within the coating additive layer. The Hf-rich particles and the effect of heat treatment on the particles are also discussed. © 2011 Elsevier B.V. Source


Wang Y.,SIFCO Minneapolis | Suneson M.,SIFCO Minneapolis
Surface and Coatings Technology | Year: 2013

Cyclic oxidation tests were carried out on simple β-(CoNi)Al, Hafnium (Hf)-modified β-(CoNi)Al, Platinum (Pt)-modified β-(CoNi)Al+ξ-PtAl2, and Hf-Pt-modified β-(CoNi)Al coatings on Co-based Haynes-188 substrates at 1050°C in air for up to 4670h to identify the effects of Hf doping. The results showed that the β-(CoNi)Al coating reached 0.55mg/cm2 weight gain at 1960h and became unstable, resulting in massive spallation at the sample edges; the Hf-(CoNi)Al coating exhibited stable weight gain up to 4520h followed by a rapid weight increase, corresponding to the formation of Cr- and Mn-containing spinel phases. Both Pt-(CoNi)Al+ξ-PtAl2 and Hf-Pt-(CoNi)Al coatings showed stable weight gain for the duration of the test. Examination of the surface and cross-section microstructure by Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectroscopy (EDS) indicated that the original coating was completely transformed into a γ-(CoNiCr) phase in the (CoNi)Al and Hf-(CoNi)Al coatings, leading to the formation of Cr2O3 scales or spinel phases. The β-(CoNiPt)Al phase persisted to the end of the test in the Pt-(CoNi)Al and Hf-Pt-(CoNi)Al coatings, showing dense, adherent Al2O3 scales. The oxidation resistance from the best to the worst can be ranked as: Hf-Pt-(CoNi)Al or Pt-(CoNi)Al>Hf-(CoNi)Al>(CoNi)Al. © 2012 Elsevier B.V. Source


Wang Y.,SIFCO Minneapolis | Suneson M.,SIFCO Minneapolis | Sayre G.,SIFCO Minneapolis
Surface and Coatings Technology | Year: 2011

With small additions of Reactive Elements (RE), such as hafnium (Hf), to aluminide coatings applied on aircraft turbine engine components, the adherence of the protective oxide scale to the coatings and the oxidation resistance of the coatings at high temperatures can be significantly improved. At SIFCO, Hf-modified aluminide coatings, Hf-Pt-modified aluminide coatings on Ni-base superalloys and the industrial-scale production of Hf-modified aluminide coatings on different aircraft turbine engine components were successfully developed. Surface morphology and cross-section microstructure of the developed coatings were inspected and compared by using a Scanning Electron Microscope (SEM) equipped with energy dispersive spectroscopy (EDS), and Glow-Discharge Mass Spectrometry (GDMS). Experimental results showed that Hf was successfully incorporated and precipitated Hf-rich particles were observed on the coating surface, along grain boundaries within the additive layer, and at the interface between the additive layer and the interdiffusion layer. Finally, Hf-rich particles as well as Hf solubility are discussed. © 2011 Elsevier B.V. Source

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