|کد مقاله||کد نشریه||سال انتشار||مقاله انگلیسی||ترجمه فارسی||نسخه تمام متن|
|5023071||1470245||2018||12 صفحه PDF||سفارش دهید||دانلود رایگان|
- Coefficient of thermal expansion and residual stresses of coatings measured by optimized optical implementation of the substrate curvature method
- Different nanostructures obtained by PLD result in different residual stresses and coefficient of thermal expansion.
- Nanocrystalline tungsten coatings show a higher compressive residual stress than amorphous like ones.
- The coefficient of thermal expansion is strongly correlated to the crystallites dimension.
- Amorphous like tungsten coatings have higher coefficient of thermal expansion than nanocrystalline tungsten ones.
The in plane coefficient of thermal expansion (CTE) and the residual stress of nanostructured W based coatings are extensively investigated. The CTE and the residual stresses are derived by means of an optimized ad-hoc developed experimental setup based on the detection of the substrate curvature by a laser system. The nanostructured coatings are deposited by Pulsed Laser Deposition. Thanks to its versatility, nanocrystalline W metallic coatings, ultra-nano-crystalline pure W and W-Tantalum coatings and amorphous-like W coatings are obtained. The correlation between the nanostructure, the residual stress and the CTE of the coatings are thus elucidated. We find that all the samples show a compressive residual state of stress that decreases as the structure goes from columnar nanocrystalline to amorphous-like. The CTE of all the coatings is higher than the one of the corresponding bulk W form. In particular, as the grain size shrinks, the CTE increases from 5.1 10Â â6 KÂ â1 for nanocrystalline W to 6.6 10Â â6 KÂ â1 in the ultra-nano-crystalline region. When dealing with amorphous W, the further increase of the CTE is attributed to a higher porosity degree of the samples. The CTE of the coatings is also investigated as function of materials stiffness: when stiffness decreases, the CTE increases.
Journal: Materials & Design - Volume 137, 5 January 2018, Pages 192-203