Search for dissertations about: "Precipitates"

Showing result 1 - 5 of 122 swedish dissertations containing the word Precipitates.

  1. 1. Precipitate stability in creep resistant 9-12% chromium steels

    Author : Ardeshir Golpayegani; Chalmers University of Technology; []
    Keywords : growth; precipitates; coarsening; atom probe field ion microscopy APFIM ; energy filtered TEM EFTEM ; 9-12% chromium steel;

    Abstract : 9-12% chromium steels are used extensively in modern steam power plants at service temperatures up to 600°C. These materials are subjected to creep deformation during exposure which is the limiting factor in increasing the steam temperature and thus the thermal efficiency of the plants. READ MORE

  2. 2. Precipitation Reactions at High Temperatures in 9-12% Chromium Steels

    Author : Mats Hättestrand; Chalmers University of Technology; []
    Keywords : thermo-dynamical simulations; creep resistant; 9-12% chromium steel; energy filtered TEM; precipitates; atom probe field ion microscopy; quantitative metallography;

    Abstract : This thesis reports on quantitative investigations of microstructural changes, mainly precipitation reactions, occurring during heat treatment, ageing and creep of 9-12% chromium steels. Several alloys with varying composition have been investigated. READ MORE

  3. 3. Aspects of microstructural evolution in chromium steels in high temperature applications

    Author : Åsa Gustafson; KTH; []
    Keywords : Cr-steels; nucleation; coarsening; model; DICTRA; precipitates; carbides; carbo-nitrides; MX; VN; M23C6; TiC; TEM; EFTEM; Curie-temperature;

    Abstract : In this thesis 9-12 % Cr steels, used for high-temperaturecomponents in fossil-fired power plants are considered. Thecreep strength of thees steels depend on their microstructurethat consists of a matrix of tempered lath martensite withdensely distributed precipitates. READ MORE

  4. 4. Toward first-principles understanding of carbonitride precipitation in steels

    Author : Dan Fors; Chalmers University of Technology; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Steels; Coarsening; Interfaces; Peierls-Nabarro model; Diffusion; Precipitates; Density functional theory; Dislocation network; Misfit; Electronic structure;

    Abstract : The most important and widely used group of metallic alloys is steels, whichare alloys of the element iron together with carbon and usually other elementssuch as B, N, V, Nb and Cr. The strength in these alloys is closely connectedto the distribution of point defects, precipitates and grain boundaries whicheffectively act as obstacles for dislocation migration. READ MORE

  5. 5. Theoretical studies of boron and transition-metal carbonitride additions in steels

    Author : Dan Fors; Chalmers University of Technology; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Electronic structure; Dislocation network; Interfaces; Peierls-Nabarro model; Density functional theory; Steels; Coarsening; Diffusion; Misfit; Precipitates;

    Abstract : Martensitic 9-12%Cr steel alloys are today widely used as critical components in fossil-fired steam power plants with steam temperatures up to 600°C, where sound oxidation resistance and excellent creep strength are required. Their strength and long-term creep resistance are closely connected to the presence and stability of Cr-rich M23C6 (M = Cr, Fe) carbides and densely distributed MX precipitates (M = transition metal, X = C or N), which effectively act as obstacles for dislocation migration. READ MORE