Ph. D. THESIS

265 Pages·2010·48.34 MB·English

CRANFIELD UNIVERSITY
ADRIANA ENCINAS-OROPESA
A STUDY OF HOT CORROSION
OF SINGLE CRYSTAL SUPERALLOYS
COATINGS.
AND PLATINUM-ALUMINIDE
100,5
AND MANUFACTURING
SCHOOL OF INDUSTRIAL
SCIENCE
Ph. D. THESIS
CRANFIELD UNIVERSITY
SCHOOL OF INDUSTRIAL AND MANUFACTURING SCIENCE
Ph. D. THESES
ACADEMIC YEAR 2005
ADRIANA ENCINAS-OROPESA
A STUDY OF HOT CORROSION
OF SINGLE CRYSTAL SUPERALLOYS
AND PLATINUM-ALUMINIDE COATINGS.
SUPERVISORS: Professor J. R. Nicholls, Dr. N. J. Simms
October 2005
@Cranfield University, 2005. All
No be
rights reserved. part of this publication may reproduced
without the written perrnýission of the copyright holder.
W" ji! iaw inspiration for
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Acknowledgments
The like her European
to to the
author would express gratitude
Commission for funding Advanced Long Life
the this the
of work under
Turbine Coating Systems (ALLBATROS), ENK5-
project contract number
CT2000-00081 the European Coal Steel Community (ECSC)
and and with
7220-PR/053.
project number
I have had in both
the the
pleasure of working a very nice environment,
National High Temperature Surface Engineering Power Generation
the
and
Technology Centre, I for help, kindly
where anybody asked someone always
helped I learning
the
me. greatly appreciate patience shown on my slow
English language I However, I like
the to
process of ever since started. would
I have bothered
thank the the
especially people most:
John Nicholls for believing in by
Professor the
me giving me
in his
to this thorough
opportunity work project, guidance and constructive
discussions.
Dr Nigel Simms, had time for doubts, for his
who always my guidance
for I have leamt I
the things
and all since started working with
and support
him.
John Oakey, Boýa Arias, Paul Kilgallon, Andrew Potter, Steve
Nigel Legrave, Jim Norton, helped
Mabbutt,
all of whom me at some point of
Rachel Newton, her help during
the
this work. who always offered
(and
this
part of project always ended up weighing samples),
experimentation
Grasa-Adiego
Gemma the time to to
who made and effort study and explain
looked impossible Peter West
to
understand, and who often was
me what
I for
time this thesis.
with my work so could make
overloaded
Tim Pryor, taught helped the laborious
who me and me with set up of
in laboratory, keep
the to them time them
the start on and going.
experiments
Andrew Dyer, taught to the to
who me prepare samples correctly and make
(and for fixing
the
use of equipment my mistakes).
proper
Suzie Chadwick in for her
the time
computer centre nice support every
because I The kind ladies
I the the
messed up my work on computer. of
panic
help find information just
library to that
who me often, was under my nose and
for her in Procite
Heather the
to
support use.
The Community Development Centre, Margaret Lynn, for
and making
life lovely difficult
those
easier and all gestures of support and care on and
happy
times...
I like have had
this to thank those
would opportunity people who a
influence during formation,
they
great my academic/professional since provide
the to the Professor Cristina Oliviera
me with means cope with unknown: who
taught to "organize thoughts, to think... " Don Julio Giovine
me my not who
"engineering be ingenious " Cuco Navajas
taught me that means... to and who
"... do I have?... "...
told the the t
me what and qualite of executan
I to friends I have hours
am also very grateful my with whom spend
hours fun, have been happy for
those
and of reflexion, adventure and whom
I
thank them
me, and will personally.
in
To brothers, Armando Alberto in
my
my y whom retrospective,
has
both because Atlantic
there the
nicest memories, you are always and
...
bond
made our closer and stronger...
To father; for being his
my my maestro and example, advice, support
and encouragement.
love,
To friend, Isidro for his
care and
mi greatest unconditional
...
because I feel lucky have in life for
support... very to coincided and sharing
life
my with you...
And little "moon light "... Itzel, for
to those
my all extraordinary
feelings day...
you give me with your smile every
Sincerely
Adriana Encinas Oropesa
Abstract
At the time, for (e.
present combined cycle systems power generation g.
IGCC), increased lower
offer efficiency of power generation and
C02, SOxg, NO,,, being
environmental emissions, specifically and as well as
fossil fuels. Economic factors,
to
the the
adaptable most such as cost of
be Materials influence lifetime in
the the
materials must considered. service
Solid fuels like biomass
required operational environment. coal and produce
different
that,
combustion environments containing a range of contaminants
they their
when reach melting points, may cause accelerated corrosion,
directly life
the time the turbine
affecting service of gas constructional
This is known Hot Corrosion.
materials. accelerated corrosion as
The develop, influence
this to the
aim of study was an understanding of
factors hot
these turbine
of environmental on rate of corrosion of modem
i. CMSX4 SC2 both
the the
materials, e. single crystal alloys uncoated and
,
PtAl that for turbine blade in
coated are needed a gas and vanes operating a
hot in lGCC
range of corrosion environments expected an plant.
To this laboratory tests
achieve aim, a series of corrosion was planned
in industrial high
to the temperature
simulate same corrosion environment as
Following for
testing,
turbine
operation. established procedures corrosion
gas
in
furnace
to
samples were exposed a controlled atmosphere a mix of gases
(air/SO241CI) 50 100h duration. Each
time
with a cyclic exposure of and/or
be
to to
cycle, samples were removed recoated with an alkali salt mixture a
500h 1000h. Cross by
time
total
exposure of and or sections were examined
SEM/EDX to identify the hot To the
mode of corrosion attack. quantify rate of
this
corrosion, samples were measured pre-exposure and post-exposure, and
data
was statistically assessed.
corrosion
from data, life
Finally, this
quantitative prediction models were
developed to describe/predict the hot the
onset of corrosion and corrosion rates
different deposition fluxes, both
under gas compositions, and various
observed
I II hot in incubation
typical type type temperatures terms
at and corrosion of
Separate have been developed for
the two
periods. models
and propagation
CMSX4 SC2, in both
the
single crystals superalloys: and uncoated and
The fit defined by
platinum aluminide coated condition. goodness of as the
from 0.88 0.99 for
to the
regression coefficient varies propagation models at
700 900'C. The incubation 7001C but less
and models are as precise at precise
9001C 0.78-0.94.
at with regression coefficients of
I
Table Contents
of
INTRODUCTION
1
..........................................................................
2 LITERATURE REVIEW
4
...............................................................
2.1 Power Generation Systems 4
................. . .............. ......................... ................. . ......
2.2 Contaminants in Coal/biomass Fired Gas Turbine 8
a
. ............. . .......... . ..............
2.3 Materials Impact the Industrial Gas Turbines 11
on
........ . ...................... . ...........
2.3.1 Introduction 11
.........................................................................................................
2.3.2 Superalloys 12
..........................................................................................................
2.3.3 Nickel-Base Superalloys 12
.....................................................................................
2.3.4 Chemical 13
composition
.........................................................................................
2.3.5 Structure Microstructure 14
and
...............................................................................
2.3.6 Effects Alloying Elements 17
of
..............................................................................
2.4 High Temperature Oxidation 19
.............................. . .......... ..................................
2.4.1 Introduction 19
.........................................................................................................
2.4.2 Thermodynamics Oxidation 19
of
...........................................................................
2.4.3 Kinetics Oxidation: Oxide Scale Formation Grown 21
of and
................................
25
2.4.4 Transport
mechanisms
........................................................................................
2.5 High Temperature Corrosion 26
... . ....... . ... . ............................. . ............... . ...........
2.5.1 Introduction 26
.........................................................................................................
2.5.2 Hot Corrosion 26
......................................................................................................
2.5.3 Hot Corrosion Degradation Sequence 27
.................................................................
2.5.4 The Initiation Stage Hot Corrosion Attack 29
of
.....................................................
33
2.5.5 Hot Corrosion: Type I Type 11
and
......................................................................
35
2.5.6 The Propagation Stage Hot Corrosion
of
............................................................
2.5.7 Thermodynamics 36
.................................................................................................
2.5.8 Basic Fluxing 40
......................................................................................................
2.5.9 Acid Fluxing 43
.......................................................................................................
2.5.10 Salt Component-Induced Hot Corrosion 49
........................................................
2.5.11 Effect Chlorine Species Hot Corrosion 50
of on
.................................................
2.6 Protective Coatings 54
................................................................................................
2.6.1 Introduction 54
.........................................................................................................
2.6.2 Coating Requirements 54
.........................................................................................
2.6.3 High Temperature Coatings 56
................................................................................
2.6.4 Alurninising 59
.........................................................................................................
2.6.5 Modified Aluminide Coatings 60
.............................................................................
2.6.6 Platinum Aluminide Coatings 60
.............................................................................
2.6.7 Microstructure PtAl Modified Coatings 62
of
.........................................................
2.6.8 Overlay Coatings 63
.................................................................................................
2.6.9 Oxidation Hot Corrosion Coatings 65
and of
...........................................................
2.7 Application Statistics to High Temperature Corrosion 67
of
..................................
3 EXPERIMENTAL
PROCEDURES 68
.............................................
3.1 Introduction
68
............................................................................................................
ii
70
3.2 Materials
. ....................
...........................................................................................
71
3.3 Corrosion Furnaces Environment
and
....................................................... ...... ..
3.4 Corrosion Testing: Deposit Re-coat Test Method in Controlled Atmosphere
72
Furnaces
................................................................................................................................
75
3.5 Metrology
. ....................
..........................................................................................
77
3.6 Specimen Manufacture
..........................................................................................
77
3.7 Pre-exposure Metrology
........................................................................................
79
3.8 Post-exposure Sample Preparation
.......................................................................
80
3.9 Post- Metrology
exposure
........................................ . ............................................
82
4 RESULTS
......................................................................................
82
4.1 Introduction
............................................................................................................
82
4.2 Mass Change
...........................................................................................................
83
data (Phase 1)
4.2.1 Mass
change
.................................................................................
83
4.2.1.1 Uncoated IN738 LC 700* C:
at
.............................................................................................................
85
4.2.1.2 Platinum aluminised coated IN738 LC:
................................................................................................
88
4.2.1.3 Uncoated CMSX-4 at 700*C:
...............................................................................................................
90
4.2.1.4 Platinum Aluminized coated CMSX-4 at 700*C:
.................................................................................
93
4.2.2 Mass data (Phase 2)
change
.................................................................................
93
4,2.2.1 Mass change on CMSX-4 (uncoated and with a PtAl coating)
............................................................
97
4.2.2.2 Mass change on SC2 (uncoated and with PtAl coating)
.......................................................................
10 1
4.3 Optical Microscopy
. .................
....................................................................
101
4.3.1 Damage Morphologies (Phase 1)
......................................................................
102
4.3.2 Damage Morphologies (Phase 2)
......................................................................
104
(Phase 3)
4.3.3 Damage
morphologies
.......................................................................
119
Statistical Assessment Hot Corrosion Data
4.4
of
...................................................
121
4.4.1 Probability Analysis Phase I
.............................................................................
121
Gas
4.4.1.1
composition sensitivity
................................................................................................................
127
4.4.1.2 Deposit
composition sensitivity
..........................................................................................................
127
4.4.1.3 Temperature
sensitivity
.......................................................................................................................
130
4.4.2 Probability Analysis Phase 2
.............................................................................
130
4.4.2.1 Sensitivity to gas composition and temperature
.................................................................................
145
4.4.2.2 Sensitivity to deposition flux
..............................................................................................................
159
5 DISCUSSION
..............................................................................
159
5.1 Introduction
..........................................................................................................
5.2 Effect Varying Deposit Flux in Different Hot Corrosion Environments 161
of
....
5.3 Effect Varying the Deposit Composition 167
of
............................... . .......... . ...........
5.4 Effect Alloy Composition Different Hot Corrosion Environments 172
of
..............
5.5 Effect the Gas Composition in Different Hot Corrosion Environments 182
of
.....
194
5.6 PtAl Coatings Performance in Different Hot Corrosion Environments
..........
III
211
5.7 Life Prediction Models in Hot Corrosion Environments
..................................
211
5.7.1 Incubation Models
.............................................................................................
214
5.7.2 Propagation Models
..........................................................................................
221
6 CONCLUSIONS
.........................................................................
223
FOR FUTURE WORK
7 SUGGESTIONS
..................................
224
REFERENCE LIST
239
APPENDIX
IV
List Figures
of
Figure 2.1: Primary by fuel 1990 2001 in
to the
consumption produce, and
United Kingdom [5] 4
. ..................................................................................
Figure 2.2: Historical Evolution Power Plant Efficiency [10] 5
of
. .....................
Figure 2.3: Simplified flow Integrated Gasification
the
sheet of process of
Combined Cycle Power Generation [14] 7
. ..................................................
Figure 2A Variation levels S02 IS03 temperature
of equilibrium Of with as
in [26] 10
refereed
. ........................................................................................
Figure 2.5: Equilibrium (Na + K)
alkali chloride vapour concentration as
function for PFBC [24] 10
temperature
of gas conditions
............................
Figure 2.6: Example blade for (a)
turbine
of a gas power generation systems
damaged (b) 12
and severely
.........................................................................
Figure 2.7: Elements important in the [32].
constitution of nickel-based alloys
14
..................................................................................................................
development
Figure 2.8: Panorama the
of of nickel superalloy microstructure
both deleterious [30] 15
showing useful and phases
.....................................
in
Figure 2.9: Microstructure the two this
of single crystal alloys studied work:
in fully heat SC2 [37] b)
treated typical
a) y' precipitates superalloy
CMSX4, in
microstructure of with y'-Nl3AI grains, embedded a 7-Ni
[38] 16
matrix
................................................................................................
Figure 2.10: Schematic diagram illustrating the for Ni-
oxidation mechanism
[39] 17
Cr-Al
alloys
. .....................................................................................
2.11: Ellingham/Richardson diagram. Standard free
Figure
energy of
formation function temperature [45] 20
of selected oxides as a of
...............
Figure 2.12: Schematic illustration the
of main phenomena and part-processes
in
the
taking place reaction of metals with single oxidant gases, e. g.
21
oxygen[50]
. .............................................................................................
for high
Figure 2.13: Interfacial transport temperature
reactions and processes
(a) (b) [49] 22
mechanisms cation mobile and anion mobile
oxidation
. ......
Figure 2.14: Schematic illustration the (e. thickness)
of variation of x g. oxide
for linear logarithmic [45] 23
time
parabolic, and oxidation
with
................
Figure 2.15: Order-of-magnitude for the
parabolic rate constants growth of
[49] 24
oxides
several
. ..................................................................................
Figure 2.16: (a) Transport through by lattice
processes scales growing
diffusion. (b) Transport in in lattice
terms
processes growing scale of and
defects, interstitial ions
e. g., of metal vacancies and and of
electronic
holes [50]
25
and electron respectively
electrons
. ........................................
Figure 2.17: Binary diagram for Na2S04-K2SO4 [65] 27
equilibrium system
......
Figure 2.18: Schematic weight change versus time to illustrate that the
degradation initiation
of corrosion resistant systems consist on an and
[6 1]..............................................................................
28
propagation stage
V