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.
The thermal behavior of CMAS-infiltrated thermal barrier coatings
Abstract Understanding the mechanisms by which the durability and functionality of thermal barrier coatings (TBCs) are compromised by the infiltration of molten calcium–magnesium alumino-silicates (CMAS) requires an assessment of the effects on the thermal and mechanical properties of the coating. This study focuses on quantifying the effect of CMAS on the thermal properties and heat transport in TBCs. The thermal properties of a 7 wt.% yttria-stabilized zirconia (7YSZ) TBC deposited on a superalloy substrate by air plasma spray (APS) were measured before and after CMAS infiltration. A rise in both volumetric heat capacity and thermal conductivity of the coating was observed upon infiltration. Calculations to explain these trends were performed for a model TBC system and found to be in good agreement with the measured results. The evolution of the phase constitution of the coating was analyzed by Raman spectroscopy and the integrity of the interface was characterized by optical examination of cross sections. These tests determined that the coating remained in good contact with the substrate and experienced no phase change after infiltration.
Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 ? 1 Rib Cotton Knitted Fabrics
This study investigates the impact of yarn count and stitch length of 100% cotton knitted fabrics. 1 × 1 ribs structured fabrics were used in this research work. The stitch length 2.50 mm, 2.52 mm, 2.60 mm, 2.70 mm, 2.80 mm and 2.96 mm were used of the yarn count of 26Ne, 28Ne and 36Ne. The areal densities of the grey fabrics were in various amounts. The impacts of yarn count and stitch length were measured concerning pilling resistance, abrasion resistance, and shrinkage and tightness factor. The result showed that the fabric pilling grade decreased while number of cycle increased. Abrasion resistance decreased but length wise shrinkage increased despite the fact that the stitch length increased. The results also exposed that the tightness factor of the fabric increased with the increase of the stitch length in both dyeing and washing state and finished state compared to grey state for the yarn count 26Ne and homogeneous result not found for yarn count 28Ne and 36 Ne. Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 × 1 Rib Cotton Knitted Fabrics