|
|
HIGH - TEMPERATURE CREEP BEHAVIOUR OF CAST COBALT-BASE SUPERALLOYS
Dvořák, Jiří ; Král, Petr ; Kvapilová, Marie ; Hrbáček, Karel ; Sklenička, Václav
Two cast and heat-treated NbC and TaC – strengthened cobalt superalloys have been developed for a precision casting of spinner discs for glass wool industry. In this work constant load creep tests in tension were carried out in argon atmosphere at three testing temperature 900, 950 and 1000 °C and at the initial applied stresses ranged from 40 to 200 MPa. All the tests were continued until the final fracture. The results of creep testing were combined with microstructural and fractographic examinations by means of light and scanning electron microscopy. A mutual comparison of creep characteristics of the investigated superalloys under comparable creep loading conditions showed that NbC-strengthened superalloy exhibited longer creep life than TaC-strengthened one. Further, it was found that carbide precipitation is the primary strengthening mechanism in both cobalt-base superalloys under investigation and the amount, morphology\nand type of carbides have the decisive effect on the creep properties including creep damage and fracture processes. By contrast, NbC-superalloy exhibited a more brittle character of creep fracture mode than TaCstrengthened superalloy. This study was initiated to investigate in more details creep deformation processes and the effect of the creep microstructure and damage evolution on both investigated superalloys. The different behaviour and properties of studied superalloys were explained based on the received results of this study.
|
|
|
Lomová houževnatost hornin a vliv rychlosti zatěžování v módu I
Vavro, Leona
The presented paper presents another results of the rocks fracture toughness measurement. The influence of the loading velocity on the fracture parameters was investigated. The loading velocity was continually changed in values 1; 0,1 a 0,01 mm/s. The measurements were realized on selected rocks in the laboratory conditions in the Institute of Geonics AS CR.
|
|
|
Aparaturní vybavení pro měření lomové houževnatosti hornin
Vavro, Leona
Při zkoumání chování hornin během jejich porušování pomocí geomechanických metod lze pozorovat vznik a šíření trhlin. Popisem trhlin jakožto nespojitostí se zabývá lomová mechanika. Příspěvek je věnován vývoji metodiky měření lomové houževnatosti hornin v podmínkách laboratoří Ústavu geoniky v Ostravě s důrazem na přípravu zkušebních těles a testovacího zařízení.
|
|
| |
host ::
RSS.