The influence of yttrium addition on thermogravimetric behaviour of new Co-10Al-5Mo-2Nb Co-based superalloy
Silesian University of Technology, Institute of Materials Engineering, 40-019 Katowice, ul. Krasińskiego 8, Poland
Silesian University of Technology, Department of Extractive Metallurgy and Environmental protection, 40-019 Katowice, ul. Krasińskiego 8, Poland
Characterization of oxidation resistance of new type of cobalt based superalloys were presented in this investigations. As a referential material the Co-10Al-5Mo-2Nb (at.%) was used as the tungsten-free version of basic Co-7Al-7W alloy. The investigated alloy was modified by addition of yttrium on the level of 0.5 at.% due to expectation of improvement of it oxidation resistance. Both Co-based superalloys were casted in Institute of Materials Engineering of Silesian University of Technology in Poland. The oxidation performance of alloys were made during thermogravimetric investigations at temperature range from 25 to 1200°C. The main analyzed parameter was mass gain detected continuously during the test. After the test the overall and cross-sectional analysis of specimens was made. They included analysis of oxide layer morphology on the surface of specimens with characterization of phase constituent of oxide layer. The detailed analysis of oxidized layer was made by scanning electron microscopy method where distribution of alloying elements was made with special attentions on yttrium localization after the test in oxide zone. Obtained data showed that addition of Y has a strong influence on oxidation performance of new Co based superalloy. Those influence is demonstrated mainly by different morphology of final oxide zone with strong influence on Mo and Nb diffusion.
Keywords: new type of cobalt based superalloys, Co-Al-Mo-Nb, yttrium influence
2018, Vol. 61, nr 11, pp. 328-332
Effect of cycling on hydrogen diffusivity in LaNi4.5Co0.5 composite electrode using constant potential discharge techniques
Czestochowa University of Technology, Faculty of Production Engineering and Materials Technology, Department of Chemistry
Two constant potential discharge (CPD) methods, corresponding to long- (> 2000 s) and short time discharge (100 - 500 s) from full cathodic hydrogenation (CPD-LT and CPD-ST methods) have been applied to evaluate atomic hydrogen diffusivity in LaNi4.5Co0.5 powder composite electrodes cycled in 6M KOH solution. The apparent diffusion coefficients of H ( EMBED Equation.3 ) are generally greater for CPD-ST method. What is more, the nature/ direction of changes of with cycling is different for the both methods: EMBED Equation.3 decreases with cycle number (N) in case of CPD-LT method and increases for the CPD-ST one. The reasons of such reverse behavior are discussed in terms of material fragmentation caused by cycling and interaction of material passivation products with hydrogen.
Keywords: Hydride material, hydrogen diffusivity, electrode cycling, corrosion products
2018, Vol. 61, nr 11, pp. 333-337
Thermal diffusion zinc coating technology with reactive atmosphere recirculation.
Part 1: General description of technology and structure of coatings
Politechnika Śląska, Gliwice, Instytut Inżynierii Materiałowej, ul. Krasińskiego 8, 40-019 Katowice
REMIX S.A., ul. Poznańska 36, 66-200 Świebodzin
The article presents an innovative thermal diffusion zinc coating technology. The technology involves recirculation of reactive atmosphere, which ensures homogenization of its composition, intensified zinc saturation in steel surfaces and increased efficiency of active agents. That newly developed technology allows creating continuous coatings on threaded elements of requested depth while at the same time considerably shortening the heating time compared to traditional sherardizing method and thus resulting in better quality of coated surface. The coatings created with the innovative thermal diffusion zinc coating technology have a two-layer structure of Fe-Zn intermetallic phases. Right at the base a compact layer of Γ1 (Fe11Zn40) phase is created and then covered with a layer of δ1 (FeZn10) phase.
Keywords: thermal diffusion zinc coating, zinc coating, sherardizing
2018, Vol. 61, nr 11, pp. 338-345