GEORG Geothermal Workshop 2016 SESSION B3, Midstream. Presentation title: Plasma Coated Steel for Geothermal Environment

1. 16 SEE/2014
1
Composite Plasma Coating Steel to Use
in Geothermal Condition
1 Metav- R&D, Bucharest, 31 C.A.Rosetti St, 020011, Romania
2“Politehnica” University Bucharest, 313, Splaiul Independentei, 60042, Romania.
3 Tehnoid Com Ltd.,48 Baritiu St, 011295, Romania.
4 Innovation Center Iceland-ICI, Arleyinir 2-8 Reykjavik , Iceland.
5Orka Náttúrunnar,110 Baejarhals , Iceland.
6 Vélvík ehf, 110 Hofðabakka, Reykjavik, Iceland.
Aurelian Buzăianu1, Ioana Csáki2, Petra Moţoiu3, Kolbrun Ragna Ragnarstottir4,
Kristjan Leosson4, Adalsteinn Arnbjornsson4, Saemundur Guðlaugsson5, Daniel
Guðmundsson6

2. 16 SEE/2014
Acknowledgements
This work is supported by the Romanian Grant EEA Financial Mechanism Committee 2009-
2014 and Iceland as Donor Stat. Bilateral Agreement Program Iceland – Romania: „Research
within priority sectors”- Contract 16 SEE /30.06.2014 – GEOTUR Project.
Geothermal Iceland areas with
temperature exceeding 2500C
at 3 km depth.
Geothermal Romania areas with
temperature exceeding 1400C
at 3 km depth.
Iceland Romania

3. 16 SEE/2014
University POLITEHNICA of
Bucharest Materials Science &
Engineering Faculty
TEHNOID – Romanian SME Partner
METAV R&D – Project
Coordinator

4. 16 SEE/2014
Innovation Centre Iceland (ICI)
Keldnaholt facility, Reykjavik
Our Nature (ON) power
plant
VÉLVÍK EHF -Precision
machining

5. 16 SEE/2014
Turbine MHI rotor at Iceland Hellisheiði
power plant
Main problem:
Defects in the coating surface
allow turbulent eddies to form
Undercutting of the
protective film
Damaging of the
protective film
Beginning the undercut
of the protective film

6. 16 SEE/2014
Fig.1 Rotor erosion from water trapped in
interstage area.
Fig.4. Water erosion damage on exhaus
side on first stage nozze inner port wall.
Fig.2 Rotor eroded from scale deposition
Fig.3.Abrasive erosion of trailing edge of
diaphragm vane caused by debris in steam.

7. 16 SEE/2014
preventing
corrosion
SOLUTIONS:
providing
good reliability
ceramic materialsmetallo-ceramic

8. 16 SEE/2014
Plasma spray process and schematic representation of
METCO-4MP plasma jet metalizing device
Plasma spray process

9. 16 SEE/2014
The specific experiments are related to the synthesis of new complex powder
mixtures with different addition of Ni-Cr components and powder elements such
as: Si-B-Al and 3.5 %WC to obtain complex-ceramic protective layers.
Commercial base metal powders
• Cr (7-12 μm-99.5% pure);
• Ni (4-8μm-99.5% pure);
• Al (4.5μm-97.5% pure);
• B (2-4μm-99.5% pure).
Plasma process (ASP&HVOF)

10. 16 SEE/2014
Powders analysis
Elements Ni Cr Si B Al Fe O
Composition (wt
%)
65.78 20.09 5.50 2.04 0.52 4.47 1.60
Chemical composition of the base complex powders.
Characteristics of powder Apparent density Flow rate Sizing
Ni20Cr5Si2B0.5Al
and 3.5W
4.2g/cm3 3.3s/50g -43/+20µm
(mesh -330//+20µm)
Feature of the characteristics of complex powders
Powders flowing rate
under atmospheric conditions

11. 16 SEE/2014
SEM image of the cross-section morphology of the
powder particles. The image shows the nano-size
elemental powder distributed in the atomized particle
SEM of complex powders Ni-Cr-B-Si-Al base.
Gas atomized, rounded to spherical in shape
particles with relative smooth surfaces.
Powder microstructure analysis

12. 16 SEE/2014
Presence of boron depresses the melting temperature and contributes to the formation of
hard phases. Silicon is added to increases the self-fluxing properties, and NiCrSiBAl alloys
are widely used because of the good resistance of boride, carbide and silicide solid phase to
wear and steam corrosion.
EDX spectrum analysis of complex
Ni-Cr-B-Si-Al powder particles.
Plasma HVOF parameters and EDX analysis
Gas Volume flow [SLPM]* Operating pressure
[MPa]
Oxygen 250-350 1.0
Propane 40-80 0.05
Air 450-600 0.07
* SLPM = Standard Liters per Minute Gas
consumption.
Characteristics of experimental HVOF samples deposition

13. 16 SEE/2014
The coating HVOF spray samples on substrate stainless
steel 4307 (304L) to test the complex matrix composites
deposition in different geometrical shapes.
SEM image of multi-composite protection
surface coating 65Ni20Cr5Si2B0.5Al
X 500
Plasma HVOF coating analysis

14. 16 SEE/2014
Optimization of spraying parameters and stress relaxation processes will be as important as
fixed thickness of steel deposition and properties cermets composite.
Oxygen
[l/sec]
Propane
[l/sec]
Air
[l/sec]
Carrier gas
pressure
Series 1 [atm]
Carrier gas
pressure
Series 2
[atm]
Carrier gas
pressure
Series 3
[atm]
4.5 1.2 8 8.8 10.2 11.5
The experimental powder deposition and main specification of HVOF process
HVOF coating analysis
The Series 3 sprayed from at distance of 150 mm have the highest values of micro-
hardness followed by the sample Series 3, that was sprayed at 200 mm.
Microstruture of the deposition layer
Ni-Cr-B-Si-Al

15. 16 SEE/2014
The micro hardness of multi-composite coating 65Ni20Cr5Si2B0.5Al obtained
in variables spray distances and operating pressures conditions
Microhardness results

16. 16 SEE/2014
XRD analysis
 Were observed the major cubic Cr6Ni16Si7 and tetragonal phases Cr0.7Ni0.3, - with
the effects in carburizing and chlorination resistance.
 Were observed to the minor orthorhombic phase Ni3B similar cemented structure
and similar properties of silicides - chemically stable and inert.
 The increase of Si content up to 5.50%, results in the presence of chromic silicides
Cr5Si3.
 A higher content of Si and B significantly lowers the plastic properties of the
composite layers.

17. 16 SEE/2014
The SEM analysis confirming the crystalline and fine size;
The Cr0.7Ni0.3 improves adherence increase resistance of oxide layer, and hence
improves oxidation, sulfidation and carburization resistance.
Scanning electron micrograph of a tipical coating composites plasma deposition powders
used for thick-film (2) Ni-Cr-Si-B-Al and Ni-Co-Cr as a sub-layer (1)
2
1
HVOF coating results

18. 16 SEE/2014
 Formation of the protective coating oxide layer with plasma HVOF deposition is a practical
way to decrease their oxidation and the corrosion rate of the geothermal turbines
components. Thermal plasma deposition of Ni, Cr, B, Si or Al coatings form the stable
oxides with low diffusion coefficients for oxygen.
 The complex matrix composites greater corrosion and oxidation resistance and maintain
hard hardness, strength and wear resistance up to operating geothermal steam
conditions.
 The spray distance is an important parameter to be considered for tuning the processing
conditions and thus to maintain or even improve the adhesion of the coatings.
Conclusions

19. 16 SEE/2014
Thank you for your attention!
http://metav-cd.ro/geotur/