The internal oxidation (IO) of Ag - VC composites containing 5 vol.% of carbide was examined at three oxidation temperatures (350, 400, 600 °C). Two mechanisms were observed due to the formation of double oxides with relativelylow melting points. At temperatures below the lowest eutectic point in-situ, or diffusion less IO, was observed with the formation and growth of oxide layers surrounding the initial carbide. At temperatures above the eutectic point IO resulted in the formation of liquid oxide pools, which grew in size and developed into a network of oxides within the metal matrix. The kinetics confirmed the presence of two distinct mechanisms.
COBISS.SI-ID: 14376214
The creep behaviour of 9Cr-1Mo-0.2V (P91-type) steel was studied at elevated temperatures of 625 to 675 °C. Uniaxial creep tests were performed under constant load and constant stress at initial stresses of 120 to 240 MPa. For description of creep behaviour of P91-typ steel the improved stress-dependent, energy-barrier model was successfully used. The Monkman-Grant relation showed that the minimum creep strain rate is not quite inversely proportional to the time-to-rupture for both constant-load and constant-stress creep tests.
COBISS.SI-ID: 1073759
In this work the results of microstructural, fractographic and XRD analysis of heat-resistant austenitic stainless steel (AISI 310) were shown. Testing of the steel pipes was carried out after long life application steel pipes for supply of the hot air (between 2 and 3 years) at temperatures from 600 to 650oC. SEM and XRD results are shown that microstructure consisted from sigma-phase, carbides and austenite matrix which reduced on chromium. It was found that composition of sigma-phase on any places in investigated steel was 45,5%Cr-34,8%Fe-9,5%Ni-5,5% Si (wt. %). Fracture surface of steel after long life application is transgranular brittle fracture.
COBISS.SI-ID: 1156959