DBPapers
DOI: 10.5593/sgem2011/s06.113

MICROSTRUCTURE CHANGES DURING CREEP DEFORMATION OF G 20Mo5 STEEL

AUTHOR/S: Z. KOVACEVIC, Z. KARASTOJKOVIC, R. PERIC, M. MLADENOVIC
Monday 1 August 2011 by Libadmin2011

11th International Multidisciplinary Scientific GeoConference SGEM2011, www.sgem.org, SGEM2011 Conference Proceedings/ ISSN 1314-2704, June 20-25, 2011, Vol. 2, 89-96 pp

ABSTRACT

Creep damage of pressure equipment involves a great variety of high temperature
components ranging from superheaters, boiler drums, furnaces, reactors, etc.
Consequences of failures of these components are of high economic and safety concern.
Moreover, the probability of failure of high temperature components is now increasing
due to frequent cyclic of power plants imposed by a deregulated market and the search
for increasing temperatures in ultra supercritical plants.

A housing from high-pressure steam turbine in power plant is projected in order to meet
construction period 100000-200000 of operating hour. Housing is produced by casting.
Such after long-term servicing, the surface layer at housing is changed under the
influence of pressure and temperature in creeping conditions. For improve the
evaluation precision of creep damage of steam turbine casings at thermal power plants,
the microstructures of casing materials are examined.

NDT during service are a fundamental tool for residual life assessment as well. The
material from cast housing is observed metallographically by means of the replica
technique. In this paper is presented an evaluation of microstructure the housing highpressure
steam turbine castings in viewing into the microstructure changes, according to
the recommendations of the European Commission, using light microscopy. The paper
also includes a short description of the replica method.

Keywords: creep damage, microstructural changes, light microscopy, replica method