1. PROCESSING AND CHARACTERIZATION OF PLASMA SPRAY COATINGS OF INDUSTRIAL WASTE AND LOW GRADE MINERAL ON METAL SUBSTRATES Presented by: Ajit Behera Presented by: Ajit Behera National Institute Of Technology, Rourkela

2. Presentation Outlines: 1.Background 2.Objective 3.Experimental Methods 4.Morphology of Raw material & Product 5.Results 6.Conclusions 7.References National Institute Of Technology, Rourkela

3. 1. Background Surface Engineering: The properties desired at the surface are different from those at the bulk of the component. This is the reason for use of surface engineering. Coating: When material is deposited over another material or the same material, it is referred to as Coating. Coating may be applied as liquids, gases or Solids. National Institute Of Technology, Rourkela

4. Plasma: Plasma is the fourth state of matter. As heat is added to this substance it melts into a liquid at its melting point (see phase change), boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons are so energized that they leave their parent atoms from within the gas. National Institute Of Technology, Rourkela Ionization Deionization Vaporization Condensation Liquid Solid Gas Plasma Melting Freezing Sublimation Deposition Energy Level

5. It is a part of thermal spraying. (In this processes in which finely divided metallic and non-metallic materials are deposited in a molten or semi- molten state on a prepared substrate) This plasma is created by striking an electric arc between tungsten cathode and copper anode inside the plasma torch. Plasma Spraying National Institute Of Technology, Rourkela

6. Evaporation Ion Plating Cathod Arc Deposition Electron Beam Physical Vapour Deposition Sputtering Deposition Pulsed Laser Deposition Vacuum Deposition Metal-organic Vapour Phase Epitaxy Flame Electric Arc Electrostatic Spray Assisted Vapour Deposition Plasma Arc Low Pressure Plasma Flame Arc Deformation Diffusion Welding Laser Ionization Liquid Spray DIP Process Fluidized bed Sol-Gel National Institute Of Technology, Rourkela

7. Aim is for processing and characterizing plasma spray coating by using industrial waste and low grade ore (i.e Fly- Ash+Quartz+Illmenite mixture as coating material) on Copper and Mild Steel Substrates. 2. Objective National Institute Of Technology, Rourkela

8. Fly-ash, quartz, Illmenite was taken with 60:20:20 weight percentage ratio. The powders are mechanically milled in a planetary ball mill for 3 hours for homogenization of mixture to get approximately 40-100 µm size. Substrates are Mild steel and Copper having dimensions 1 inch diameter and 3 mm thickness. The specimens were grit blasted to increase surface roughness. substrate surface cleaned by acetone and plasma spraying immediately carried out. Spraying process is dc non-transferred arc mode atmospheric plasma spray. Input power of plasma gun was varied from 11 to 21 kW by controlling the gas flow rate. The powder deposition process carried out at 90 0 spraying angle. 3. Experimental method National Institute Of Technology, Rourkela

9. Morphology of powder/raw material for coating: Figure 4.1 SEM micrographs of fly ash+quartz+illmenite mixture which is to be coated. National Institute Of Technology, Rourkela 4. Morphology of Raw material & Product Top View of Prepared Samples: Figure 4.2 Top view of the product of this project.

10. 5. Results Surface Morphology: Figure 4.3 Mild Steel substrate Sprayed at 11kW power level. Figure 4.4 Mild Steel substrate sprayed at 15kW power level. Molten/semi-moltel particle agglomerated to form laths. More amount of cavitations observed. Inadequate flow of molten particles Some spheroidal splats are found. Cavitations found in inter- granular boundaries. National Institute Of Technology, Rourkela

11. Larger diameter Splats formed due to increase in power level. lesser cavitations found. Uniform distribution. All particles becomes fully-molten before strike on the surface. Particle gets more thermal energy. Very less cavitations found. More Uniform distribution. Figure 4.5 Mild Steel substrate sprayed at 18kW power level. Figure 4.6 Mild Steel substrate sprayed at 21kW power level. Cont… National Institute Of Technology, Rourkela

12. Interface Morphology Figure 4.7 Mild Steel substrate sprayed at 11kW power level. Figure 4.8 Mild Steel substrate sprayed at 15kW power level. Lamellar structure present with cavitations at the coating substrate interface. Some semi-molten powder particles found. Poor mechanical bonding of the coating onto the substrate observed at some places. Minimum adhesion strength. Less no of voids are present than 11kW sprayed sample. Improved mechanical bonding. Splats layers are globular, larger in dimension and equi-axed type. Some spheroidal particles are also observed National Institute Of Technology, Rourkela

13. Figure 4.9 Mild Steel substrate sprayed at 18kW power levelFigure 4.10 Mild Steel substrate sprayed at 21kW power level. Good coating-substrate interface bonding. Porosity decreased. Better mechanical as well as metallurgical inter-locking throughout the length of coating. Larger diameter splats. Inter-layer gaps/pores are found. Metallurgical bonding occurred at the interface. Cont… National Institute Of Technology, Rourkela

14. X-RD Analysis Figure 4.11 XRD-Analysis of different coating specimen & raw material. National Institute Of Technology, Rourkela

15. Coating Adhesion Strength Figure 4.12 Comparison of adhesion strength of mild steel and copper with respect to power level. Bond strength of coating interface evaluate by using coating pull out method confirming to ASTM C-633. It is found that, adhesion strength increses with increase in operating power level up to a certain level of torch power and there is no such improvement of adhesion strength with further increasing in power level. For Mild Steel the maximum of 6.56MPa at 21kW power level and for Copper 6.32MPa. National Institute Of Technology, Rourkela The fracture mode is adhesive if it takes place at the coating-substrate interface and that the measured adhesion value is the value of practical adhesion.

16. Coating Deposition Efficiency Coating deposition efficiency is defined as the ratio of the weight of coating deposited on the substrate to the weight of the expended feedstock. Weighing method is accepted widely to measure this. It can be described by the following equation Where, η is the deposition efficiency. Gc is the weight of coating deposited on the substrate. Gp is the weight-expended feedstock. Figure 4.13 Variation of deposition efficiency of fly-ash+quartz+illmenite coatings at different power levels. National Institute Of Technology, Rourkela Maximum 48% deposition efficiency for Mild Steel substate. Maximum 43% deposition efficiency for Copper substate.

17. Coating Thickness Figure 4.14 Variation of coating thickness of fly ash+quartz+illmenite coatings at different power levels. Measured by using an optical microscope by taking polished section of sample. Maximum thickness of 300 μm found for mild steel. Maximum thickness of 350 μm found for Copper. Depends on thermal conductivity of specimen. National Institute Of Technology, Rourkela Hardness of the Coatings Figure 4.15 Variation of coating hardness of fly ash+quartz+illmenite coatings at different power levels. Measurement is carried out with Leitz Micro- Hardness Tester using 50Pa (0.419N) load. Hardness depends on formation/ transformation to their allotropic forms and their compositional variations during spray deposition with the increase in input power.

18. Coating Porosity Coating porosity measurement was done using the image analysis technique. The polished interfaces of various coatings are studied under optical microscope equipped with a CCD camera. From the digitized image obtained by this system, coating porosity was determined using VOIS image analysis software. Figure 4.16 Variation of coating porosity of fly ash+quartz+illmenite coating with torch power. The pore interconnectivity in the structure, influencing the cohesion of the deposit. with decrease in coating porosity, adhesion strength increases. In Copper coating porosity decreases from 28% to 18% with increase in adhesion strength from 4.9MPa to 6.32MPa. National Institute Of Technology, Rourkela Surface Roughness Figure 4.17 Variation of surface roughness of fly ash+quartz+illmenite coating with torch power. Surface roughness has varied from 5.2 – 11.7Ra incase of coatings made on mild steel substrate and that from 12.4 – 14.33 Ra incase of copper substrate. when there is decrease in coating surface roughness from 14.33 Ra to 12.4 Ra, then adhesion strength increases from 3 to 4.9. But in case of 18KW and 21KW, the bond strength increases with surface roughness, only due to high power level, which transfer sufficient energy to fasten at the interface.

19. ANN Prediction of Adhesion Strength Input Parameters for TrainingValues Error tolerance Learning parameter(ß) Momentum parameter(α) Noise factor (NF) Maximum cycles for simulations Slope parameter (£) Number of hidden layer neuron Number of input layer neuron (I) Number of output layer neuron (O) 0.003 0.002 0.001 1,00,00,000 0.6 8 5 1 Table 4.7 Input parameters selected for training (Coating adhesion strength). Figure 4.18 The three layer neural network for adhesion strength. National Institute Of Technology, Rourkela Predicted adhesion strength compare with experimental results based on different feed rate Figure 4.19 Comparative plot of experimental and ANN predicted values of adhesion strength (Plasma spray at 12 gm/min feed rate and 100 mm torch to base distance). Figure 4.20 Comparative plot of experimental and ANN predicted values of adhesion strength (Plasma spray at 18 gm/min feed rate and 140 mm torch to base distance).

20. Prediction results based on different powder particle size Figure 4.21 Predicted adhesion strength vs Power level for Copper by change in size of powder (Plasma spray at 12 gm/min feed rate and 100 mm torch to base distance). Figure 4.22 Predicted adhesion strength vs Power level for Mild Steel by change in size of powder (Plasma spray at 12 gm/min feed rate and torch to base distance 100mm). Prediction results based on torch to base distance Figure 4.23 Predicted adhesion strength vs torch to base distance for Copper by change in size of powder (Plasma spray at 18kW power level and 12 gm/min feed rate). Figure 4.24. Predicted Adhesion strength vs torch to base distance for Mild Steel by change in size of powder (Plasma spray at 15kW power level and 12 gm/min feed rate and). National Institute Of Technology, Rourkela

21. Microstructure of Erodant Surface morphology of fly ash-quartz coating eroded with SiC erodent at different impact angles (a) (b) Figure 4.26 SEM micrographs of eroded surfaces of coatings deposited at 18 kW at angle of impact (a) 60° and (b) 90° using SiC as the erodent. National Institute Of Technology, Rourkela Figure 4.25 Morphology of Eroded Surfaces 4.4 EVALUATION OF COATING PERFORMANCE 4.4.1 Erosion Wear Behavior of Coatings by Taguchi Experimental Design Smaller is the better characteristic: Figure 4.27 Residual plot of S/N ratioFigure 4.28 Main effect plot of S/N ratio

22. Figure 4.29 cumulative mass loss of coating vs time for 18kW coating substrate at erodent impact pressure of (a) 1 bar, (b) 2 bar. Figure 4.30 Cumulative mass loss of coating vs time for 21kW coating substrate at erodent impact pressure of (a) 1 bar, (b) 2 bar. National Institute Of Technology, Rourkela (a) (b) (a) (b)

23. Operating power level of the plasma torch influences the coating adhesion strength, deposition efficiency and coating hardness and coating morphology to a great extent. The microstructure of the coatings is also dependent on the physical characteristics such as porosity, phase transformations of the coating materials during spraying at different power levels. The coating bond-strength increases with the input power to the torch up to a certain power level and further increase in input power there is no significant increase in adhesion strength. Coating adhesion is better in case of mild steel substrate than that of copper substrate. Deposition efficiency has increased in a step up fashion with the increase in torch power input. Due to phase transformations and inter-oxide formation during plasma spraying, changes in coating characteristics such as hardness etc. are observed. Hence these coatings can be recommended for tribological applications. It has been identified that, impact angle and erodent size are the most significant factors affecting the erosion wear rate of fly ash+quartz+illmenite coatings. Maximum erosion of the coatings took place at an impact angle of 90 0. Quartz, illuminate mixed with fly-ash was found to be a suitable material for depositing thermal spray coating on metals. 6.Conclusions National Institute Of Technology, Rourkela Scope for future work: The present work opens up a wide area for future investigators to explore the possibility of development of new fly-ash composite materials to ascertain further improvement in coating properties with considering cost of coating material.

24. 7. References [1] S.C. Mishra, “Analysis of Experimental Results of Plasma Spray Coatings Using Statistical Techniques”, BOOK: Advanced Plasma Spray Applications, Published by InTech, Printed in Croatia, 83-96, 2012, ISBN 978-953-51-0349-3. [2] P Fauchais, Topical Review: Understanding plasma spraying, Journal of Physics D: Applied Physics, 37, 2004, R86-R108. [3] Alok Satapathy, S.C. Mishra and D.K. Nath, P.V. Ananthapadmanabhan and K.P. Sreekumar, “Deposition of Redmud-Graphite Coating on Metals by Plasma Spraying, International Conference on Advances in Surface Treatment”, Research & Applications (ASTRA), 537-540, 2004. [4] Swapnil M.Kondawar & Mr. V.W.Khond “Fly Ash Utilization Technologies and Use as Thermal Composite Insulation”, Indian Streams Research Journal, Vol - II, ISSUE – III, 2012, http://www.isrj.net/PublishArticles/647.aspx. [5] S. C.Mishra and Alok satpathy, “Plasma spraying of red mud-fly ash mixture on metals: an experimental study”, Presented in National Conference on Materials and Related Technology, TIET, 2003, Patiala, India, http://dspace.nitrkl.ac.in/dspace/bitstream/2080/315/1/ALOK-NCMRT+2003.pdf. [6] C. N. Panagopoulos, E.P. Georgiou, A.G. Gavras, “Composite zinc-fly ash coating on mild steel”,Surface & Coatings Technology”, 204:37-41, 2009, doi:10.1016/j.surfcoat.2009.06.023. [7] S. C.Mishra, S.K.Acharya, “Weathering behavior of fly ash-jute-polymer composite”, Journal of Reinforced Plastics and Composite, vol.26, 1201-1202, 2007. [8] Jadambaa Temuujin, Amgalan Minjigmaa, William Rickard, Melissa Lee, Iestyn Williams, Arie van Riessen, “Fly ash based geopolymer thin coatings on metal substrates and its thermal evaluation”, Journal of Hazardous Materials, Vol. 180, 748-752, 2010. [9] S. Das, Thesis on: “Processing and Tribological Behaviour of Flyash-Illmenite Coating”, Department of Metallurgical & Materials Engineering National Institute of Technology, Rourkela, 2008. [10] S. Praharaj, “Processing and Characterization Of Fly Ash- Quartz Coatings”, Thesis Submitted for M.Tech Degree in Metallurgical & Materials Engineering, National Institute Of Technology, Rourkela, 2009. National Institute Of Technology, Rourkela

25. Thank You National Institute Of Technology, Rourkela