Anke Silvia Ulrich

Entwicklung von ausscheidungshärtbaren Cr-Si-Basis-Legierungen für Hochtemperaturanwendungen: Mikrostruktur und Oxidation


Front	Back

ISBN:

978-3-8440-7322-5

Series:

Schriftenreihe des DECHEMA-Forschungsinstituts
Herausgeber: DECHEMA-Forschungsinstitut
Frankfurt am Main

Volume:

Keywords:

Hochtemperaturwerkstoffe; Cr-Legierungen; Oxidation; Mikrostruktur; Modell Oxidationskinetik

Type of publication:

Thesis

Language:

German

Pages:

130 pages

Figures:

49 figures

Weight:

192 g

Format:

21 x 14,8 cm

Bindung:

Paperback

Price:

45,80 € / 57,30 SFr

Published:

April 2020

Buy:

Download:

Available PDF-Files for this title:

You need the Adobe Reader, to open the files. Here you get help and information, for the download.

These files are not printable.


	Document		Document
	Type		PDF
	Costs		11,45 EUR
	Action		Purchase in obligation and display of file - 20,6 MB (21588731 Byte)
	Action		Purchase in obligation and download of file - 20,6 MB (21588731 Byte)


	Document		Table of contents
	Type		PDF
	Costs		free
	Action		Diplay of file - 477 kB (488401 Byte)
	Action		Download of file - 477 kB (488401 Byte)

User settings for registered users

You can change your address here or download your paid documents again.

User:	Not logged in.
Actions:	Login / Register Forgotten your password?

Recommendation:

You want to recommend this title?

Review copy

Here you can order a review copy.

Link

You want to link this page? Click here.

Abstract

Heat-treatable Cr-Si-based alloys for high temperature applications with Cr ≥ 89 at.% were developed and optimized with respect to their oxidation and nitridation resistance as well as their microstructure. Therefore Ge, Mo and Pt were chosen as additional alloying elements.
All investigated alloys developed a two-phase microstructure consisting of a chromium solid solution, Crss, matrix and A15 phase precipitates, which was proven using EPMA, SEM and XRD. Depending on alloy composition and heat treatment, the fraction of A15 precipitates and thereby the alloy properties can be adjusted. Annealing at 1200°C led to a maximum A15 phase fraction of 37% with respect to the investigated alloy compositions. Si, Ge, and Pt are A15 phase formers while Mo was found in comparable concentrations in both phases. The precipitates formed in Mo-containing alloys were smaller compared to the other systems.
Oxidation tests at temperatures of 1050 - 1350°C were conducted for up to 200 h in synthetic air to investigate the alloys’ oxidation and especially nitridation resistance. For an improved description of oxidation kinetics of Cr-based alloys, a kp-kv-P-model was developed to analyse TGA measurements with mass discontinuities due to oxide scale cracking. It was found that by additional alloying with Ge, Mo and Pt both oxidation and nitridation resistance were improved in comparison to the binary system. Cr3PtN forms in the presence of Pt instead of detrimental Cr2N. Additionally, Ge decreases the effect of local scale failure on the oxidation kinetics and improves scale adhesion. Alloying with Mo enhances SiO2 formation and reduces the evaporation rate constant, most likely due to a morphological change in the Cr2O3 scale.