Mechanistic insights into the transformation processes in Z-phase strengthened 12% Cr steels
Artikel i vetenskaplig tidskrift, 2018

Compositionally complex Z-phase strengthened 12% Chromium steels are considered as potentially viable materials for components used in highly-demanding environments in steam power plants, operating at a target temperature of 650 °C. To date, however, the transformation processes of various phases into the desired precipitate, i.e., Z-phase CrTaN, are not fully understood. In this research, we first designed and produced three different alloys and then studied the microstructure in the as-tempered and aged conditions (for up to 10,000 h at 650 °C) using advanced electron microscopy, X-ray diffraction, and atom probe tomography. We report on the evolution of the densely distributed MX (Ta(C, N)) and M2X ((Cr, Ta)2N) precipitates into blade-like and bulky Z-phase, respectively. The blade-like precipitates benefit from a smaller size compared to the bulky ones, providing precipitation hardening for creep resistance. We discuss an interactive role of carbon and nitrogen content in the formation of the Z-phase. Our findings pave the way towards designing new alloys with improved properties to serve in harsh environments at 650 °C.

MX

Precipitates

M N 2

Electron microscopy

Creep

Atom probe tomography

Författare

Masoud Rashidi

Chalmers, Industri- och materialvetenskap, Material och tillverkning

Ardeshir Golpayegani

Sandvik

Saad Ahmed Sheikh

Chalmers, Industri- och materialvetenskap, Material och tillverkning

Sheng Guo

Chalmers, Industri- och materialvetenskap, Material och tillverkning

Hans-Olof Andrén

Chalmers, Fysik, Materialens mikrostruktur

Fang Liu

Chalmers, Industri- och materialvetenskap, Material och tillverkning

Materials and Design

0264-1275 (ISSN)

Vol. 158 237-247

Z phase strengthened steels for ultra-supercritical power plants (Z-ULTRA)

Europeiska kommissionen (FP7), 2013-02-01 -- 2016-01-31.

Ämneskategorier

Oorganisk kemi

Metallurgi och metalliska material

Korrosionsteknik

DOI

10.1016/j.matdes.2018.08.006

Mer information

Senast uppdaterat

2018-09-03