Papers by Keyword: Argon Atmosphere

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Authors: Kuang Hung Tseng, Kai Chieh Hsien
Abstract: The aim of the present work was to investigate the effects of specific nitrogen gas additions to argon shielding gas on morphology and microstructure of austenitic stainless steel TIG welds. An autogenous TIG welding process was applied on type 316L stainless steel to produce a bead-on-plate weld. The ferrite content of weld metal was measured using a Feritscope. The results indicated that the arc voltage increase as the amount of nitrogen gas added to the argon atmosphere increases. The retained ferrite content of type 316L stainless steel TIG weld metal decreased rapidly as nitrogen gas addition to the argon shielding gas was increased.
Authors: Jin Xue Zhang, Guo Dong Hao, Jin Li Ji
Abstract: Ceramic coatings with the main crystalline of TiO2 were prepared on Ti-6Al-4V alloy by pulsed bi-polar Micro-arc Oxidation (MAO) in Na2SiO3 solution. The coated samples were calcined in argon under 1000oC. The phase composition, morphology and element content of the ceramic coatings were investigated by XRD, SEM and EDS. The results showed that the main components of the coatings are TiO2 and amorphous substances, after oxidation in argon, SiO2 was crystalized in coating. The content of elements in the coatings both changed a little.
Authors: Guo Dong Hao, Zhao Hua Jiang, Xiao Hong Wu, Yan Hua Cao
Abstract: Compound ceramic coatings were prepared on Ti-6Al-4V allosy by pulsed bi-polar Micro-plasma Oxidation (MPO) in NaAlO2(S1) and Na2SiO3(S2) solution respectively. The coated samples were calcined in argon under 1000 oC. The phase composition,morphology and element content of the ceramic coatings were investigated by XRD, SEM and XRF. After oxidation in argon, The Al2TiO5 of S1 coating surface was decomposed into Al2O3. SiO2 was crystalized in S2 coating with the final proportion of SiO2 to TiO2 on the coating surface is 81:18. The morphology of the ceramic coatings after the calcination was also different. S1 coatings calcined in argon were fine, grains and pores were smaller and were combined tightly with the substrate, on the contrary, S2 coatings calcined in argon cracked on the coating surface and were separated with the substrate. The content of elements in the coatings both changed a little, which may be due to the reaction of the substrate in the oxidation. According to the phase composition and the morphology of the coatings, S1 coatings are better than S2 coatings.
Authors: Ruben L. Menchavez, Masayoshi Fuji, Tomohiro Yamakawa, Takeshi Endo, Minoru Takahashi
Abstract: This study investigates the phase compositions in gelcast dense alumina and porous alumina that were sintered in an inert atmosphere. Both materials were gelcasted using identical slurry composition except for adding surfactant to slurry intended for porous shaping. The resulting gelcasted samples were dried and then sintered in argon gas at 1700oC. The X-ray photoelectron analysis was used for identifying the phase compositions in sintered samples, which was supported with TG/DTA and electrical measurements. Results showed that, in addition to alumina and carbon phases, the dense sample yielded Al4C3 and Al, while porous sample yielded aluminum oxycarbides. The formation of these phases reduced the carbon content through different chemical reactions to a limited extent because they formed a protective layer on alumina grains, which prevented the direct contact between alumina and carbon. Subsequent measured electrical resistivities of dense and porous alumina were, respectively, 0.20 and 0.32 ,-cm, indicating that the carbon networks are preserved in both materials.
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