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Abstract: The microstructure and surface topography of PVD hard coatings are among the most important properties, as they significantly determine their mechanical, tribological and other properties. In this study, we systematically analyzed the microstructure and topography of a TiAlN/CrN nanolayer coating (NL-TiAlN/CrN), not only because such coatings possess better mechanical and tribological properties than TiAlN and CrN monolayer coatings, mainly because the contours of the individual layers, in the cross-sectional STEM or SEM images of such coatings, make it easier to follow topographic and microstructural changes that occurred during its growth. We investigated the effects of the substrate rotation modes on the microstructure and surface topography of the NL-TiAlN/CrN coating, as well as on the periodicity of the nanolayer structure. The influence of the substrate material and the ion etching methods were also studied, while special attention was given to the interlayer roughness and influence of non-metallic inclusions in the steel substrates on the growth of the coating. The topographical features of the NL-TiAlN/CrN coating surface are correlated with the observations from the cross-sectional TEM and FIB analysis. Selected non-metallic inclusions, covered by the NL-TiAlN/CrN coating, were prepared for SEM and STEM analyses by the focused ion beam. The same inclusions were analyzed prior to and after deposition. We found that substrate rotation modes substantially influence the microstructure, surface topography and periodicity of the NL-TiAlN/CrN layer. Non-metallic inclusions in the substrates cause the formation of shallow craters or protrusions, depending on their net removal rates during the substrate pretreatment (polishing and ion etching), as compared to the matrix.
Keywords: magnetron sputtering, nanolayer hard coatings, growth defects, surface topography, interlayer roughness, non-metallic inclusion, focused ion beam (FIB), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM)
Published in DKUM: 19.03.2025; Views: 0; Downloads: 3
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Abstract: Soil erosion is the major problem of Ethiopian highland areas where an average soil loss of 42tons/ha/year, with rate soil depth loss of more than 2 cm/year, corresponding to 1 to 2 billion US$/year (an amount comparable to the country’s annual budget). The higher soil loss has been estimated at Southern Ethiopia where densely settled on highlands. A vast majority of the population derives its livelihood from forest, livestock herding and agriculture. The economic conditions force the rural poor to exploit the environment for their survival. Keeping the importance, the work was conducted in Silti Woreda, Southern Ethiopia, with the objectives; to identify the current status and trend of soil conservation practices, to assess the socio-cultural, economic, biophysical and institutional/policy/support system constraints for the implementation and maintenance of conservation practices. The study reveals, indigenous soil conservation technologies are considered as effective methods of conservation. But, population poverty and unawareness are major constraints.
Keywords: soil conservation, agriculture, backwardness, indigenous method, topography
Published in DKUM: 10.04.2018; Views: 1174; Downloads: 124
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