Preparation of Electro-deposited Ni-Mo-Al Coating and Its Properties
Ni-Mo-Al coatings were prepared on Ni alloy by electrodeposition method. The effects of current density, frequency, duty cycle and electrodeposition time on mass percentages of Al of Ni-Mo-Al coatings were researched, respectively. The properties of wear weight loss and friction coefficients were investigated respectively. Ni-Mo-Al coatings were characterized with inductively coupled plasma-atomic emission spectroscopy (ICP-AES), energy-dispersive analyses of X-ray (EDAX), scanning electron microcopy (SEM), and X-ray diffraction (XRD) techniques, respectively. When electro-deposition parameters: current density 18.5 A/dm 2, frequency 5000 Hz, duty cycle 0.5 and electrodeposition time 20 min, mass percentages of Al of Ni-Mo-Al coating is as high as 2.04%. Ni-Mo-Al coatings show higher wear weight loss and lower friction coefficient compared with those of Ni-Mo coatings. The wear weight loss of Ni-Mo-Al coating is 1.27 times higher than that of the Ni-Mo coating. The friction coefficient of Ni-Mo and Ni-Mo-Al coatings are 0.816 and 0.540 respectively. The Ni-Mo and Ni-Mo-Al coatings have similar nodular microstructure. The nodules of Ni-Mo-Al coating are smaller than those of the Ni-Mo coating. The parts of nickel are replaced by Mo and Al respectively in the Ni lattice.
Bending fatigue failure of atmospheric-plasma-sprayed CoNiCrAlY + YSZ thermal barrier coatings
Abstract Bending fatigue failure of conventional atmospheric-plasma-sprayed CoNiCrAlY + ZrO2–8 wt.% Y2O3 thermal barrier coatings with/without the thermally grown oxide layer generated between the bond coat and the top coat was experimentally studied at room temperature. Microscopical and profilometrical characterization of as-received and fractured specimens and a simplified finite element study of cooling thermal stresses show that the same fatigue strength of both the as-coated and the oxidized specimens (i.e. its insensitivity to the presence of the thermally grown oxide) is most likely caused by a preferential through-the-thickness cracking of the thermally grown oxide layer. Moreover, the bond-coat/substrate interface is identified as the weakest part of the studied thermal barrier system under both low and high crack growth rates.
Chemical Metallurgy: Principles and Practice
Foreword. Preface. Acknowledgements. Appreciation. 1. Acquaintance. 2. Mineral Processing. 3. Thermodynamics and Kinetics. 4. Pyrometallurgy. 5. Hydrometallurgy. 6. Electrometallurgy. 7. Energy and Environment. Subject Index.