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Effect of casting conditions and heat treatment on high temperature low cycle fatigue performance of nickel superalloy Inconel 713LC
Šulák, Ivo ; Obrtlík, Karel ; Hrbáček, Karel
The present work is focused on the study of high temperature low cycle fatigue behaviour of Inconel 713LC produced by a vibratory investment casting (VIC) in as-cast conditions and in the condition after heat treatment (HT) consisting of hot isostatic pressing (HIP) followed by precipitation hardening. Low cycle fatigue tests were carried out on cylindrical specimens in symmetrical push-pull cycle under strain control with constant total strain amplitude and strain rate at 800 °C in air. Hardening/softening curves and fatigue life curves of both materials were assessed and compared with data of Inconel 713LC produced by a conventional investment casting (CIC). Cyclic hardening can be observed in the high amplitude domain while saturated stress response is apparent for low amplitude cycling for all material batches. Data presented in Basquin representation show an increase in fatigue life of both VIC batches compared to the CIC batch, however, no effect of HT on fatigue life of Inconel 713LC produced by VIC was observed. In contrast, the heat treated Inconel 713LC demonstrates slightly higher fatigue life in Coffin-Manson representation. The microstructure of both superalloys was studied by means of scanning electron microscopy (SEM). The microstructure of superalloy is characterized by dendritic grains with casting defects. It comprises the γ matrix, cubic γ´ precipitates, eutectics and carbides. The effect of the VIC and HT on fatigue performance and microstructure of Inconel 713LC is discussed.
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Optical evaluation of corrosion products using colorimetric spectroscopy
Majtás, Dušan ; Fialová, P.
Aim of this work is to test possibility to utilize colorimetric spectroscopy for monitoring the corrosion of lead and tin-lead alloys. And furthermore method suitability for preliminary corrosion evaluation of cultural heritage objects. According to literature colorimetry is used to monitor patinas of bronze objects, thus the method might be also suitable for lead based alloys. Samples used were made from commercially produced lead plate. These were exposed in the climatic chamber to different relative humidity (60, 80, 90 %). After the exposure the corrosion products with different color formed on sample surface. These corrosion products were evaluated by different methods: optical microscopy, colorimetric spectroscopy, and X-ray chemical analysis. Collected colorimetric data display difference between treatments suitable for patina evolution monitoring. The paper presents obtained results and comparison of applied methods.
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HYDROGEN SORPTION IN ORDERED Mg-In ALLOYS
Čermák, Jiří ; Král, Lubomír ; Roupcová, Pavla
Hydrogen storage (HS) performance of three Mg- x In- y CB alloys (CB - amorphous carbon, x = 55, 64, 73 y =\n10 wt%) was studied. Indium concentration covered an area of ordered β structures. Alloys were prepared by\nball-milling in hydrogen atmosphere. Kinetic curves and PCT isotherms were measured in the temperature\ninterval from 200 °C to 325 °C. X-ray diffraction spectroscopy (XRD) was used for structure investigation. Alloy\nwith x = 73 wt% In ( β ’’ structure) showed reversible amorphization during temperature cycling between about\n100 °C and 350 °C. Hydrogen sorption experiments were done by the Sieverts method under the hydrogen\ngas pressure ranging from 0.1 MPa to 2.5 MPa. It was found that hydrogen sorption capacity varied between\n0.47 and 1.1 wt% H 2 . Hydride formation enthalpy ∆H calculated from desorption PCT experiments was\nsignificantly lower than ∆H , known for pure Mg. This invoked an idea that atomic order of Mg-based HS\nmaterials might decrease the high thermodynamic stability of hydride phase.
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