Showing papers by "Sitaram Dash published in 2006"
TL;DR: In this article, laser surface modification of plasma sprayed alumina coatings were carried out for transforming metastable γ-Al 2 O 3 phase predominantly present in as-sprayed coating to a thermodynamically stable α-al 2 O3 phase.
Abstract: Surface modification and characterization of engineering components using high energy beams is an ever expanding and innovative area of research. Laser surface modification of plasma sprayed alumina coatings were carried out for transforming metastable γ-Al 2 O 3 phase predominantly present in as-sprayed coating to a thermodynamically stable α-Al 2 O 3 phase. These laser treated coatings were characterized using laser based non-destructive techniques like laser Raman spectroscopy, laser scattering, photoluminescence and piezospectroscopy for quantitative evaluation of the phase transformation, surface roughness, densification and residual stress associated with the coatings. Raman spectroscopic studies indicated the restoration of α-Al 2 O 3 phase and laser scattering technique was used to optimize the processing parameters to obtain superior surface finish. Photoluminescence measurements have shown a marginal decline in residual stress and significant increase in density of the laser treated coatings.
68 citations
TL;DR: In this article, a home-assembled TGA-MS system was used to enhance the high-temperature hardness and wear resistance of electroplated chromium on AISI 316 LN austenitic stainless steel.
Abstract: A gas-phase nitridation procedure has been investigated using a home-assembled TGA-MS system to enhance the high-temperature hardness and wear resistance of electroplated chromium on AISI 316 LN austenitic stainless steel. The sluggish diffusion kinetics of nitrogen in chromium and the presence of a thin oxide layer at the surface are the major constraints encountered during low-temperature gas nitridation process. This paper attempts to bring out a detailed correlation of the effect of nitridation environment, ammonia dissociation rate, substrate temperature and catalytic role of a thin nickel layer, on the nitriding characteristics towards addressing the above-mentioned limitations. XRD and SEM investigations on the nitrided specimens unambiguously reveal the morphology and the distribution of CrN and Cr 2 N phases formed during nitridation.
36 citations