1,721,201 research outputs found
Trattamenti termochimici superficiali degli acciai sinterizzati (nitrurazione e cementazione
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18th International Conference on Surface Modification Technologies; Dijon; 15 November 2004 through 17 November 2004; Code 67119 - Microprobe characterization of nitrocarburized surface layers.
No full textThe present study aims to analyse by microprobe the phases obtained in sintered steel samples nitrocarburized in a gaseous atmosphere at 730°C, by means of a mixture of ammonia-methanol (15%) with a previous sulfoxidizing treatment, executed with sulfur dioxide at 500°C, in order to close the surface porosity. The alloying elements in samples are: C (0.01, 0.50 and 0.76%), Ni (4 and 7%), Cr (1.5%), Mo (0.5%), Cu (0.5 and 2%) and Al (1%). The surface hardened layers present remarkable thickness and are constituted by the s solid solution, the γ′-Fe4N carbonitride, martensite and austenite. The surface layers are characterized by X-ray diffraction analyses, effected at different depth, by grinding the surface layers, in order to evaluate the relationship of the phase types and percentages with the depth in the compound layers. Microprobe analyses evidence a partition of alloying elements in the different phases, more evident in the γ′- carbonitride and in martensite than in the ε solid solution and in austenite
Corrosion behaviour assessment of cast and HIPed Stellite 6 alloy in a chloride-containing environment
No full textCobalt-base (Stellite) alloys have seen extensive use in wear environments mainly due to their high strength, corrosion resistance and hardness. Co-base superalloys rely primarily on carbides formed in the Co matrix and at grain boundaries, for their strength and wear resistance. The distribution, size and shape of carbides depend on processing conditions. Currently, the use of Stellite alloys has extended into various industrial sectors (e.g. pulp and paper processing, oil and gas processing, pharmaceuticals, chemical processing) and the need for improved information regarding corrosion of Stellite alloys has increased. It has been recognized that processing changes, which affect the microstructure of Stellite alloys, most affect corrosion resistance. In this work the corrosion behaviour of Stellite 6 alloy in the as-cast and the HIPed consolidated forms is compared and contrasted using DC and AC electrochemical techniques in static saline conditions. The results show that there is a significant difference in the corrosion performance of HIP consolidated Stellite 6 and it is possible to link the corrosion behaviour to the microstructure. The benefits of using HIPing as a manufacturing process for the corrosion performance of Stellite 6 are discussed
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