It includes, introduction of Erosion and corrosion and the problems arise from this and there possible solutions.

1. Ved Prakash Sharma
Present Affiliation B. Tech, Final year
Academic
Qualification
Pursuing B. Tech, GIT, Jaipur, Rajasthan
Area of
Specialization
Mechanical Engineering
Achievements /
Awards
Presented research paper in international
conferences : 2
Published international Journal : 1
Paper No: 253 Problems regarding Erosion-Corrosion in
Power Plants and their possible solutions: A
Review
Authors: Ved Prakash Sharma, V N Shukla
Presenting
Author Photo
Global Institute Of
Technology,
Jaipur,
Rajasthan, India

2.  Introduction (Erosion & Corrosion)
Prevention of corrosion & erosion
Thermal spray techniques
 Importance of Coating
 Requirement of protective system
Results and Discussions
Conclusion

3. Introduction
Corrosion is the degradation of material due to
chemical interaction with their environment.
According to Khanna (2005), oxidation - is the formation
of the oxide scale. If the scale spalls frequently - metal is
consumed continuously - material ultimately fails [1]
.
Erosion is the degradation of material due to
mechanical interaction with the environment.
He et al.,(2001), reported that both mechanical properties
and oxidation resistance must be considered for its use in
high temperature applications [2]
.

4.  Chatterjee et al., (2001), - Establishment and maintenance of an
impervious, stable, inert, adherent, protective layer on the substrate
during the service period [3]
.
 Heath et al., (1997), - Material damage can be controlled by including
proper alloy selection, optimum design of components, injecting chemical
additives, shielding of substrates and protective coatings [4]
.
 Eliaz et al., (2002), - Hot corrosion of gas turbine components could be
controlled by employing proper selection of structural alloys, application of
coatings [5]
.
 Priyantha et al., (2003), - An estimated 40% of total US steel
production goes to replacement of corroded parts and products [6]
.
 Cheruvu et al., (2006), – replacement cost of the hot section components
can exceed 35% of the cost of a new plant [7]
.
 Otsuka (2002), - Condensation/accumulation of low melting-point salts
from flue-gas - root cause for the severe wastage of tube materials [8]
.

5. Boiler elements highly vulnerable to erosion–corrosion
wear (Szymański et al., 2015)[9]

6. Typical examples of erosive wear in fluidized boiler: a) the area over the
ceramic lining, b) transition zone in thermally sprayed coatings, c) damage
caused by erosion of the wall, and d) damaged superheater tube.[9]

7. Importance of Coating
To achieve desired characteristics, surface modification
plays a vital role.
The use of suitable coatings provides
 Higher melting temperature
 Maintain high hardness and strength at
elevated temperatures.
 Better erosion and wear resistance
 Higher resistance to corrosion and oxidation

8. Thermal spray
technique:-
Melted particles
Voids, Porosity
Un-Melted Particles
Schematic diagram of thermal spray process, Sidhu et al., (2007) [10]

9. Coating parameters of thermal spray process (Kuroda et al.,
2008) [11]
.

10. PVD Machine, MNIT Jaipur

11. Prevention of Corrosion & Erosion
 Metal Treatment
o Alloying Elements – Add erosion-corrosion resistive
agents
o Surface Coatings - W-C, Cr-C based coatings, Zinc,
Tin etc.
 Treatment of Environment
o Removal of Erodent
o Control pH
o Removal of Oxygen
o Use of Inhibitor
 Change of Potential
o Cathodic Protection
o Anodic Protection

12. Type of Salt Deposit found on Boiler for
different fuels.
Type of fuel Typical salt deposits References
Waste ZnCl2, PbCl2, KCl, NaCl Smith et al., (2001) [12]
,
Spiegel et al., (2000) [13]
Straw KCl, K2SO4 Montgomery et al., (2000) [14]
Wood KCl, K2SO4, NaCl, Na2SO4 Henderson et al., (2000) [15]
Residual oil Na2SO4, V2O5 Luthra et al., (1982) [16]
Coal Na2SO4, K2SO4,
(Na,K)2Fe(SO4)3
Reichel et al., (1988) [17]
Viswanathan et al., (2002) [18]

13. Melting Points of Salt Deposits on Boiler
Tube (George et al.,2007) [19]

14. A CASE STUDY ON BOILER TUBE FAILURE by Prakash et al., (2001) [20]
S. NO. Type of Failure No. of Failures %age
out of 89
1 Erosion due to ash and hot 50 56.18
corrosion including overheating
due to corrosion
2 Erosion due to pulverized fuel 12 13.48
from coal nozzles
3 Welding joint cracks 10 11.24
4 Overheating due to choking 8 8.99
5 Leakage from water wall, header 5 5.62
drains due to expansion and
contraction
6 Miscellaneous 4 4.49

15. Results and Discussions

16. FE-SEM micrograph showing morphology of as-sprayed CrN
coating deposited by PVD Method on 304L Stainless Steel

17. Guru Gobind Singh Super Thermal power Plant (GGSSTPP), Roop Nagar (Punjab)

18. FE-SEM/EDS Surface analysis of bare substrate 304L
exposed to superheater of the coal fired boiler 700±10 0
C for
1000 hours.

19. FE-SEM/EDS Surface analysis of coated specimen (CrN)
exposed to superheater of the coal fired boiler 700±10 0
C for
1000 hours.

20. properties of different coatings deposited by different methods
Sr.
No.
Coating composition Deposition
method
Micro hardness Porosity
(%)
Ref.
1. Cr3C2-25(NiCr) Plasma
spray
543±43VHN <2 24
2. Cr3C2-20(NiCr) D-gun 894±35HV0.3 0.65±0.3 23
3. WC-12.5Co-1.5Cr Cold spray 963±99HV0.3 1.4-2.2 22
4. WC–10Co–4Cr D-gun 1114 ± 100HV — 21
5. WC-4 Cr3C2-12Ni HVOF 1012±90HV0.3 0.7-1.8 22

21. Hot corrosion behavior of cermet coatings deposited by different thermal
spray techniques and in different environments
Sr.
No.
substrate Coating
Composition
Deposition
method
Salt Thick
ness
(µm)
Remark Ref.
1. Superni 75 Cr3C2-NiCr D-gun 75%Na2SO4+25
%K2SO4
— Coating shows good resistance
against corrosion
25
2. UNS-
G41350
80Cr3C2-
20NiCr
HVOF 3.4% NaCl 130 Coating shows higher corrosion
resistance than the bare substrate
26
3. AISI 1010 CrNi-9.5C Plasma 3.5% NaCl 450 Diffusion of Ni into Fe at coating-
substrate interface enhance corrosion
resistance
27
4. Superni
718
Cr3C2-NiCr D-gun 75%Na2SO4+25
%K2SO4
— Oxide scale is crack free, massive
and dense cluster consisting Ni, Cr
25
5. T91 steel 75Cr3C2-
25(Ni-20Cr)
HVOF Na2SO4+60%V2
O5
325±25 Coating extended life of component
with higher corrosion resistance
28
6. 347H Cr3C2-25NiCr D-gun Na2SO4+Fe2(SO
4)3
150 Coating protect the substrate and
having porous microstructure
29
7. 347H Cr3C2-NiCr HVOF Na2SO4+Fe2(SO
4)3
225±25 Coating has good corrosion
resistance and surface scale is also
found to be intact
30
8. Superfer
800H
Cr3C2-NiCr D-gun 75%Na2SO4+25
%K2SO4
— Diffusion of Fe from substrate into
coating
25
9. T22 Cr3C2-25NiCr D-gun Na2SO4+Fe2(SO
4)3
150 Bare substrate result intense
spallation of scale due to corrosion
and coating protect the sample
29

22. Conclusion
• The corrosive species present in oil or fly ash dissolve the protective
oxide layer by chemical reactions and accelerate the corrosion.
• For protection of component against the erosion and corrosion a
composite system must be required instead of single material.
• Tungsten carbide based and chrome carbide based coatings are
suitable for erosion and corrosion respectively.
• D-gun spray method is more effective than HVOF due their high
strength, lower porosity, good bonding strength and uniformity.
• Nano-structured coatings shows better corrosion- erosion resistance
as compare to conventional coatings.
• Wear and corrosion resistance coatings is an optimum solution of
erosion and corrosion at high temperature.

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