EffEct of Slurry EroSion on cf8M turbinE StEEl

AmAndeep KumAr1 And JAsmAninder singh grewAl2

1,2Dept. of Production Engineering, GNDEC Ludhiana (India). Email: 1rajldh0001@gmail.com, 2jsgrewal23023@gmail.com

Abstract: Slurry erosion of hydro turbine steel is a common problem in hydro power station where the electric energy produced by converting kinetic and pressure energy of water by the turbine. When water comes through hills it contain abrasive particle in it and form slurry. When sand particles size increases then problem of slurry erosion, in Nozzle, gates, runner, agricultural equipment, hydraulic component, pumps increases. Number of method available to protect the material from slurry erosion. In this study slurry erosion performance of CF8M turbine steel at angle 30° was investigated. Pressure and angle remained same. We have done microstructure feature of coating by changing the stand of distance and slurry concentration. Nano-coating TiAlN (latuma) and AlCrN (pro) used to protect the material. Most extreme weight reduction occurred when stand of distance was 20mm and slurry concentration was and stand of distance varies. Most extreme weight reduction occurred when stand of distance was 20mm and slurry concentration was 20000ppm. Less erosion occurred when stand of distance was 15mm and slurry concentration was 15000ppm for both coated and bare samples. TiAlN and AlCrN samples have better erosion resistance.

Keywords: Nano-coating, Slurry erosion, Stand of Distance, Slurry concentration, Physical vapour deposition.

concentration, impact angle, pressure shape, erodient size etc.

1.1. coatings

Coating is the protective layer which is used to protect the material. Coating is the covering film which improve the base material properties. The purpose of applying coating is decorative and functional. Number of methods has been used for covering the substrate by coating. Coating increase the life of material. The purpose of developing coating on the surface of base material can be natural and artificial. Method used for coating is physical vapour deposition.

1.2. Physical Vapor deposition

Physical vapour deposition is a method which protect the material from the slurry erosion effect. PVD techniques are latest coating processes with which variety of vacuum deposition methods used to generate the lean films of coatings. Physical vapour deposition is that types coating in which material goes from three stages first goes from condense phase to vapour phase and then come back to its original stage. The generally used PVD processes are

introduction1.

Slurry erosion of hydro turbine steel is very common problem in hydro power station where electric energy is produced by converting the kinetic energy and pressure energy of water by the turbine blades. When the water comes from hills number of sand particles mix with water and form slurry. Slurry concentration increase during the rainy days because in rainy days presence of sand particles and stone in water goes high resulting in loss of turbine steel material (Goyal et. al., 2012). When the sand particle size increase then the problem of slurry erosion, in nozzle, gates, runner, agriculture components, pumps, hydraulic components increases. In slurry erosion high pressure water with or without sand particle strikes the material it deteriorates the material. Due to this process of erosive wear, life of equipments decrease and economic loss increase (Abbade et. al., 2000). Slurry means mixture solid and liquid. Solid means particles of sand, silt, gravel, cement, etc. Slurry erosion is a material loss process in which solid particles present in water responsible for erosion. There are number of parameter which have great affect on the slurry erosion i.e., slurry

I J M S E © Serials Publications

8(2) 2017 : July-December • pp. 161-165

162 Amandeep Kumar and Jasmaninder Singh Grewal

sputtering and evaporation. PVD techniques provide thin film for mechanical, optical, and chemical and electronic items. Common industrial coating which are mostly used by PVD are titanium nitride, zirconium nitride, chromium nitride, Titanium aluminium nitride. Physical vapour deposition techniques have anti sticking properties of tool thereby improving the performance of material exposed to wear conditions (cadena et. all., 2013). PVD is a metal deposition process and active gas like nitrogen, oxygen, or methane has been used.

1.3. dc Magnetron Sputtering

DC magnetron method is that types of process of PVD in which highly energetic ion of argon gas take place on the surface of material on which coating has to cover the surface. High speed collision between target and argon ion and remove the material atoms into the free space where from these atoms goes on the surface of substrate and gets condensed on the surface of substrate. This atoms after condensing on the surface form a layer of thin film. The thickness of the surface film can be controlled by managing the time of the process. PVD-DC magnetron sputtering is a method of covering the substrate with required material using plasma, where material is ejected and charged particles reacted with target surface. In this vacuum chamber inert gas of argon goes through one side with certain pressure and argon ion gets ionize due to high pressure. After this when argon ion ionize it move toward the target material with potential difference few hundred to thousands electron. Then argon ion strikes the target material which is in the condensed phase after striking the target material comes out towards the substrate. There is some gap between the cathode and anode potential difference applied to cathode and anode. This process continuously work and argon ion strikes with target material and bombardment action takes place. The atoms and molecules of the target material are fully set down on the surface of the substrate and atomic level bonding take place between substrate and coating material. After this process the material which deposited becomes stable part of the base material.

1.4. coatings deposited using Physical Vapor deposition

Many types of coatings are present to protect the material from degration process. The coatings used

for present research work are AlCrn (pro) and TiAlN (latuma). Alcrona based coating have capacity to bear high temperature 1100°C. Apart from this multi layer AlCrN coating have micro hardness 3200HV, and have low coefficient of friction 0.35. Many researcher have found that multi layer coating have high hardness (kumar et. al., 2007). TiAlN (latuma) ia also have great advantage this coating have high aluminium content with which it superior oxidation resistance and have outstanding chemical stability. TiAlN has hardness 3300HV and thickness 1 to 7 micrometer.

MatErial2.

CF8M AISI 316L material used in this present research work. This is a molybdenum steel with enhanced resistance to pitting by solution with chlorides and other halides. These groups produced tensile and creep and stress-rupture strength in higher temperature application.

EXPEriMEntal dEtailS3.

The rectangular size 17mm ¥ 15mm ¥ 6mm was prepared for experimental work. The sample was cut with proper size and polished with alumina powder for better coating adhesion between substrate and coating. The layer of aluminium chromium nitride and titanium chromium nitride was deposited.

table 1 chemical composition

Actual Nominal

C Max 0.08 0.050

Mn Max 1.50 1.68

SI Max 1.50 0.340

P Max 0.04 0.031

S 0.04 0.016

Cr 0.04 17.240

Ni 17.0 11.77

Mo 21.0 2.600

Fe balance balance

cf8m alcrn tialnfigure 1: Samle before experiment

Effect of Slurry Erosion on CF8M Turbine Steel 163

The natural sand was taken to perform the experiment. The natural sand was mixed with water. The quantity of silt was measured with parts per million method. Maximum 15000ppm to 20000ppm slurry concentration mixed with water. Slurry erosion testing was performed at 30°. Process parameter of experiment was maintained. Stand of distance and slurry concentration varied. Parameter like angle and pressure remained constant. Total number of four experiment was performed with uncoated sample, further performed eight experiment with AlCrN and TiAln coating. Samples were weighted before and after the experiment. Stand of distance 20mm and 25mm were used to conduct experiment. All the experiment was performed with slurry erosion testing machine. Slurry erosion testing machine have its own part which is used to control the parameter. Pressure control valve used to control the pressure and flow control valve used to control the flow of slurry. With this experiment weight of all the samples was measured.

figure 2: External view of slurry erosion tester

table 2 Parameter

Parameter Slurry C SOD Pressure Angle

SET A 15000 20 25psi 30°

SET B 15000 25 25psi 30°

SET C 15000 20 25psi 30°

SET D 15000 25 25psi 30°

This table show the parameter of experiment.

rESult and diScuSSion4.

During the examination of both the coating TialN and AlCrN gave good quality and appear to be black in colour. During the visual examination of both the coating there is no carck found. Shape of material

change after the experiments. Different samples gave different shape.

figure 3: bare sample after experiment

The shape of coated sample of AlCrN and TiAlN is better as compared to the bare sample after experiment.

figure 4: alcrn sample after experiment

figure 5: tialn sample after experiment

DC magnetron coating technique used to produce both the coating on the surface of the sample which have porosity less than 0.1%. Also by using the coating thickness of coating was measured by thickness gauge. Alcrona has 8-10 micro meter and TiAlN has 5-10 micrometer. SEM/EDAX analysis of both the sample was measured. First measured the SEM/EDAX analysis of bare sample to check the coating properties. After this analysis was measured of highly erosive sample. Before experiment SEM/EDAX show better result both the coating deposited properly and there was no crack found on the surface of the material. Image of sample was proper. After the experiment SEM/EDAX result showed iron particle because after two hours coating remove at a small extent so iron particle showed in the analysis.

figure 6: SEM/EdaX image of alcrn

164 Amandeep Kumar and Jasmaninder Singh Grewal

figure 7: SEM/EdaX image of tialn

figure 8: SEM/EdaX alcrn image of weared sample

figure 9: SEM/EdaX tialn image of weared sample

ALCRN-6

Operations: Smooth 0.150 | ImportALCRN-6 - File: ALCRN-6.RAW - Type: 2Th/Th locked - Start: 5.000 ° - End: 100.004 ° - Step: 0.029 ° - Step time: 114. s - Temp.: 25 °C (Roo

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X ray diffraction of alcrona sample

After this weight loss of all the sample was measured. All the samples have different weight loss. XRD of the coated sample was also measured to check the atomic structure. x ray diffraction showed proper arrangement of crystal lattice structure.

TIAIN-5

Operations: Smooth 0.150 | ImportTIAIN-5 - File: TIALN-5.RAW - Type: 2Th/Th locked - Start: 5.000 ° - End: 100.004 ° - Step: 0.029 ° - Step time: 95. s - Temp.: 25 °C (Room) -

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Weight reduction was measured time to time. The most extreme weight reduction occured when the stand of distance was 20mm and the slurry concentration was 20000ppm.

table 3 comparison of Wear Sample

S.No. Piece Sod Slurry c i.w f.w w.l

1 Cf8m 25mm 15000 9.359 9.230 0.128

2 TiAlN 25mm 15000 10.108 9.998 0.011

3 AlCrN 25mm 15000 9.766 9.710 0.056

4 Cf8m 20mm 15000 9.042 8.893 0.149

5 TiAlN 20mm 15000 9.868 9.851 0.017

6 AlCrN 20mm 15000 10.079 10.019 0.060

7 Cf8m 25mm 20000 9.502 9.304 0.198

8 TiAlN 25mm 20000 9.261 9.242 0.019

9 AlCrN 25mm 20000 9.469 9.403 0.066

10 Cf8m 20mm 20000 9.189 8.943 0.245

11 TiAlN 20mm 20000 9.816 9.788 0.028

12 AlCrN 20mm 20000 9.351 9.772 0.079

Effect of Slurry Erosion on CF8M Turbine Steel 165

After performing the bare sample, coated samples of latuma was performed. The most extreme erosion of latuma tests occurred when stand of distance was 20mm and slurry concentration was 20000ppm.But the erosion resistance of TiAlN was better as compared to both the sample. AlCrN also showed high erosion rate when the atand distance was 20mm and slurry concentration was 20000ppn. It was found that abrasive particle increase in liquid then increase in erosion rate. On the other hand decrease in stand of distance increase in erosion rate.

concluSion5. The coating by physical vapour deposition process are set up to be deposited fruitfully. TiAlN coating is better one. AlCrN is better erosion resistance properties. The maximum erosion rate occurred when stand of distance was 20mm and slurry concentration was 20000ppm.

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