Creep behavior and microstructure of a Ta-added 9%Cr steel with high B and low N contents

E Tkachev,A Belyakov

doi:10.1088/1757-899x/1014/1/012055

Abstract

The creep behavior and microstructure of an advanced a Ta-added 9%Cr steel were investigated. The steel is characterized by increased strength in the long-term creep regime, which can be associated with fine dispersion of (Nb,Ta)(C,N) particles. Strengthening of the studied steel due to the fine MX particles was estimated using the Orowan particle strengthening model.

Highlights

High-chromium martensitic steels are the primary material for the manufacture of high-temperature elements of modern coal-fired power units
It was shown that an increase in the boron content and additional alloying with tantalum can increase the dispersion of M23C6 and MX particles, and thereby increase the creep strength of the steel [3]
This study examines the microstructure and creep behavior of a 9% Cr martensitic steel with an additional amount of boron and tantalum

Summary

Introduction

High-chromium martensitic steels are the primary material for the manufacture of high-temperature elements of modern coal-fired power units. It is known that the creep strength of martensitic steels can be significantly increased by reducing the initial size and coarsening rate of the second phase particles [1-3]. It was shown that an increase in the boron content and additional alloying with tantalum can increase the dispersion of M23C6 and MX particles, and thereby increase the creep strength of the steel [3]. No studies have been carried out on the creep behavior and the distribution of secondary particles in Ta-alloyed steels with a low N content. This study examines the microstructure and creep behavior of a 9% Cr martensitic steel with an additional amount of boron and tantalum

Materials and methods

Results and discussion

The number density Ns was calculated as