CONFERENCE PREVIEW
Materials Technology for
Fossil Power Plants
This article summarizes
several papers to be
presented at the
Sixth International
Conference on
Advances in Materials
Technology for Fossil
Power Plants.
Turbines in ultra-supercritical
fossil power plants must be able
to function in extremely
corrosive environments at high
temperatures and pressures
T
he net thermal efficiency of fossil plants has improved from 33% high-heating
value (HHV) in the case of the aging fleet of “subcritical plants,” to nearly 42%
HHV for supercritical plants operating under steam conditions of 1100°F/3600
psi (593°C/25 MPa). To boost efficiencies above 45% HHV, research and development
projects are being carried out in Europe, the United States, and Japan on Ultrasupercritical (USC) powerplants. These are now emerging around the globe, and are based
on operation above 1100°F/3600psi). Even higher temperature operation is possible in
Advanced Ultrasupercritical (A-USC) power plants that can operate at steam conditions of 1300°F/4000 psi (700°C/28 MPa) and above.
The key enabling technology that drives high-efficiency power plants is the development of advanced materials and coatings with a considerable increase over traditional alloys in creep strength and corrosion resistance. Major strides have been
made in 9 - 12% chromium ferritic steels, austenitic
stainless steels, and now nickel-base alloys for these
applications.
Optimization of component fabrication processes
such as forming, welding, casting, and forging are a
critical factor in serviceability of these alloys. To continue the promotion of information exchange between scientist and engineers on an international
scale, the Electric Power Research Institute announces the Sixth International Conference on Advances in Materials Technology for Fossil Power
Plants.
Paper topics include new boiler and steam turbine materials, high-temperature material behavior
(creep, creep-fatigue, etc.), life management, fireside
and steam-side corrosion, welding and fabrication,
and field experience.
ASM and EPRI will publish the conference proceedings, building on a library of past proceedings,
including the fourth conference in 2004 at Hilton
Head Island, South Carolina; and the fifth conference in 2007 at Marco Island, Florida.
Below are some excerpts of papers that will be presented:
Processing of Advanced Alloys for A-USC Steam Turbine Applications
Paul D. Jablonski, Jeffery A. Hawk, Christopher J. Cowen, National Energy Technology
Laboratory, Albany, Oregon; and P.J. Maziasz, Oak Ridge National Laboratory, Oak Ridge,
Tennessee
The high temperature components within conventional coal fired power plants are
manufactured from ferritic/martensitic steels. To reduce greenhouse gas emissions,
the efficiency of pulverized coal steam power plants must be increased. The proposed
steam temperature in the Advanced Ultra Supercritical (A-USC) power plant is high
enough (760°C) that ferritic/martensitic steels will not work, due to temperature limitations of this class of materials; thus Ni-based superalloys are being considered. However, cast nickel-based superalloys that possess high strength, creep resistance, and
weldability are not available. To address these issues, cast analogues of selected wrought
nickel-base superalloys have been produced, for example H263, H282 ,and N105. We
will discuss our alloy design criteria, processing experiences, the as-processed and heattreated microstructures, and selected mechanical properties, as well as the prospects
for full-scale development.
In Situ Corrosion Testing of Ultrasupercritical Tube and Weld Overlay Materials
E. S. Robitz, J. M. Tanzosh, The Babcock & Wilcox Company, Barberton, Ohio
The U.S. Department of Energy and the Ohio Coal Development Office are spon30
ADVANCED MATERIALS & PROCESSES • APRIL 2010
soring the “Boiler Materials for Ultrasupercritical Coal Power Plants” program. It is aimed at identifying, evaluating, and qualifying the materials for the
construction of critical components for
coal-fired boilers capable of operating at
much higher efficiencies than the current
generation of supercritical plants. As part
of the program, B&W performed in situ
fire-side corrosion tests in the superheater bank of the Unit 1 boiler at Reliant
Energy’s Niles Plant in Niles, Ohio. Unit
1 burns a high sulfur coal, which results
in a boiler environment that is a rigorous
test for candidate tube materials. Two superheater test sections were exposed
within the boiler starting in early 2004,
and were removed for analysis in September 2007. Analysis of the samples
from both test sections permitted a comparison of the fire-side wastage rates for
the various candidate tube materials and
weld overlay combinations. The analysis
also included documentation of the morphology of the scale/metal interface for
these samples. Worst case wastage rates
showed the benefit of the EN72 weld
overlay regardless of the substrate
through the tested temperature range,
(i.e. 547°C to 664°C, 1016 to 1228°F). Inconel 740 proved to have the lowest
wastage rate among the monolithic tube
materials tested.
The Effect of Heat Flux on the
Steam Oxidation Kinetics and
Scale Morphology of Low Alloy
Materials
A.T. Fry, L. J. Brown, and J. P. Banks,
Materials Division, National Physical
Laboratory, Teddington, United Kingdom
The design of next-generation boilers, driven by the need to increase the
efficiency for carbon reduction and capture, is pushing conventional materials
to their limits in terms of both strength
and oxidation resistance. Consequently,
more expensive, higher-alloyed materials are being considered for components
usually manufactured from loweralloyed materials. Many of these materials may not have an in-service track
record to provide guidelines on how
they may behave in these aggressive environments. Laboratory tests are there-
Sixth International Conference
on Advances in Materials Technology for
Fossil Power Plants
August 31 — September 3, Santa Fe, New Mexico
Sponsored by the Electric Power Research Institute
www.epri.com
Conference Co-Chairs:
R. Viswanathan (rviswana@epri.com)
D. Gandy (davgandy@epri.com)
J. Shingledecker (jshingledecker@epri.com)
fore necessary to evaluate and certify
them.
Conventionally, simple test
coupons are subjected to corrosion tests
under isothermal conditions. While this
does provide a guide, it is somewhat
simplified and removed from reality.
Therefore, a test method has been designed for tubular specimens, and it has
been demonstrated with both laboratory air and steam as the cooling
medium.
This paper describes the design of
the heat flux test and the results of initial work on 15Mo3 under air and steam
conditions. In addition, further work on
oxides formed on 2¼Cr material both in
the laboratory under heat flux and
isothermal conditions will be examined
to establish whether the effect seen in
the 15Mo3 material is reproduced in
other alloys. The laboratory-formed
scales will also be compared to those
formed on service exposed components
to establish the reproducibility of inservice conditions.
Creep and Creep-Fatigue Behavior
of Grade 92 Base Metal and
Welded Joints
Y. Takahashi - Central Research Institute of
the Electric Power Industry (Japan);
D. Gandy – EPRI (USA)
Grade 92 steel is regarded as the
strongest material within a group of
creep-strength-enhanced steels for
supercritical fossil power plants. However, not much information has been
obtained regarding its performance in
creep-fatigue conditions. To develop reliable methods to estimate the life of
crack formation under creep-fatigue
loading, a collaborative work has been
started. Thick pipes with a circumferential weldment were tested, and many
kinds of tests have been conducted on
the base metal as well as cross-weld
specimens. Data from various tests will
be presented in comparison with the results previously reported on other steels
such as Grade 91 and 122. Results of a
preliminary assessment of life prediction will also be shown.
Small Punch Testing for
Time-Independent and Time
Dependent Mechanical Properties
Jude Foulds, Clarus Consulting LLC,
Charlotte, North Carolina
Over the last thirty years, the small
punch or miniature disk bend test has
evolved from simple empirical applications for assessing material embrittlement, to relatively complex test and test
data interpretation methods that include
evaluation of time-dependent creep rupture properties and finite element stress
analyses. The small size of the specimen
makes the test particularly suited to evaluating in-service equipment via nondisruptive small material sample removal. However, the size and specimen
configuration also provide a means of
measuring local material properties as
part of an advanced materials development effort. Applications in this case
may include mechanical (including
creep) characterization of zones of a
weldment, measurement of coating
properties such as high-temperature
ductility, and thickness-dependent properties determination. The paper summarizes the development and current status
of the testing technology, and highlights
areas of application.
ADVANCED MATERIALS & PROCESSES • APRIL 2010
31