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Characterization of γ and γ' Phases in 2nd and 4th Generation Single Crystal Nickel-Base Superalloys
Maciej Zietara,Steffen Neumeier,Mathias Göken,Aleksandra Czyrska-Filemonowicz 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.1
A Ni based single crystal superalloy from the 2nd generation, PWA 1484, and one from the 4th generation, PWA 1497, were comparatively studied by scanning electron microscopy, energy dispersive X-ray spectroscopy and nanoindentation technique in an atomic force microscope (NI-AFM) after high temperature creep deformation. During primary creep of both generations of superalloys, γ' precipitates start to coalesce and grow directionally. Further creep deformation leads to the topological inversion and coarsening of the rafted microstructure. The NI-AFM technique was used for measurements of the hardness of the γ and γ' phases in as-received and creep deformed samples in various conditions. The g matrix of the PWA 1497 superalloy is on average 0.8 GPa harder than that of PWA 1484 that can be explained by higher content of Re and Ru, since they partition predominantly to the matrix phase.
Tomasz Moskalewicz,Marcin Kot,Sigrid Seuss,Aleksandra Kędzierska,Aleksandra Czyrska-Filemonowicz,Aldo R. Boccaccini 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.1
Nano-hydroxyapatite/chitosan (nc-HA/chitosan) composite coatings were produced on two phase (α+β) Ti6Al7Nbtitanium alloy substrates by electrophoretic deposition (EPD). The microstructure of the coatings was examinedby scanning- and transmission electron microscopy methods as well as by X-ray diffractometry. The coatings,770 nm - 800 nm thick, were uniform, without any cracks or presence of large voids and they exhibited good adhesionto the titanium alloy substrate. The microstructure of the coatings consisted of nc-HA needle-like particleshomogeneously embedded in a chitosan matrix. The deposited coatings exhibited good adhesion to the substrate. The best adhesion to the titanium alloy was determined for the coating deposited from suspensions containing4 g/L of HA at 10 V during 240 s. The results confirm EPD as a convenient method to develop uniform and crackfreenanoscale organic-inorganic composite coatings on two phase titanium alloy substrates with potentialapplication in orthopedic and dental implants.
Tomasz Moskalewicz,Slawomir Zimowski,Bogdan Wendler,Piotr Nolbrzak,Aleksandra Czyrska-Filemonowicz 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.2
Duplex surface treatment, which combines the oxygen diffusion hardening with a deposition of low frictionMoS2(Ti,W) coating, was applied to improve the Ti-6Al-4V alloy load bearing capacity and tribologicalproperties. The coating (3.1 μm thick) was deposited on the oxygen hardened alloy by magnetron sputtering. Microstructure characterisation was performed by scanning- and transmission electron microscopy methods,as well as X-ray diffractometry. The results of micro/nanostructural analyses performed by high-resolutiontransmission electron microscopy showed that the coatings are composed of MoS2 nanoclustersembedded in an amorphous matrix. Some Ti α, W, and Ti2S nanocrystals were also found in the coatingmicrostructure. The wear resistance and friction coefficient of the hardened oxygen, as well as the coatedalloy, was investigated at room temperature (RT), 300 °C, and 350 °C. The presence of the MoS2(Ti,W)coating decreases the friction coefficient from 0.85 for the oxygen hardened alloy to 0.15 (at RT) and 0.09(at 300 °C and 350 °C) for the coated one. The coating essentially increases the wear resistance of thealloy at RT and 300 °C. It was found that the wear resistance of the coated alloy decreased significantlyduring the wear test performed at 350 °C.