Effect of Isothermal Ageing on Microstructure and Mechanical Behavior of 0.5Cr-0.5Mo-0.2V Low Alloy Steel
Abstract
Cr-Mo-V based low alloy steels are widely used in thermal power plants because of their
ability to withstand elevated temperature and high pressure under continuous operation. With
ferrite-pearlite and/or ferrite-bainite microstructures, these steels find their applications in
boiler tubes, pressure vessels and steam turbines. Being cost effective is one of the important
factors, which draws attention of many industrialists towards low alloyed steels over highly
alloyed steels with austenitic matrix. In this work, the microstructure and mechanical
properties degradation of low alloy steel sample were analyzed. Investigated material was in
service for 35 years. During its service life, it was exposed to high temperature and pressure
resulting in properties to undergo changes. To figure out these evident changes, sample was
solutionized and tempered for different ageing times under laboratory conditions. Changes in
the morphology of the steel microstructure such as pearlite decomposition, carbide
precipitation and spheroidisation etc. could be observed. Due to its coherent relation with
microstructure, mechanical properties were also found to have undergone variations. In order
to investigate the behavior of this steel after its exposition to different environments, hardness
and tensile tests were conducted. Microstructural evolution of the sample was observed using
SEM. TEM analysis was done to figure out the nature of carbides formed during
experimentation. Experiments revealed the improvement in mechanical properties of the steel
in the initial hours of its service due to the phenomenon of secondary precipitation. But, after
reaching its peak condition (over-ageing) deterioration in the properties started.
Cite this Article
Ranjana Kumari, Goutam Das. Effect of
Isothermal Ageing on Microstructure and
Mechanical Behavior of 0.5Cr-0.5Mo-
0.2V Low Alloy Steel. Journal of
Materials & Metallurgical Engineering.
2015. 5(3): 7–14p.
Keywords
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