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Micro-Hardness and Morphology of Cr-Coating by Mechanical Alloying

Explore the impact of ball milling on Cr-coating formation, surface properties, and uniformity. Investigate key variables like milling time and powder mass. Understand the role of mass in enhancing microhardness and surface morphology. Follow the journey from initial experimental challenges to obtaining a uniform coating. Delve into atomic force microscopy findings and physical properties of the coating powder. Discover the anomaly of Cu coating on Al substrate and the experimental solutions employed.

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Micro-Hardness and Morphology of Cr-Coating by Mechanical Alloying

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  1. Micro-Hardness Characteristics and Morphology of Cr-Coating formed due to Mechanical Alloying A.     Bakhshai, G.S. Dengler, and A.R.Torosyan Department of Physics,Goucher College, Baltimore, Maryland 21204

  2. What is Ball Milling?

  3. How Does the Reaction Propogate? • Increase in Surface to Volume Ratio • Increase in Heat as a result of the Kinetic energy of the milling balls • Cold Welding of the Powder to substrate

  4. Key Variables • Milling Time • Number and Size of Milling Balls • Powder Mass • Powder Mass to Ball Ratio

  5. Initial Experimental Problems • Downward Curvature of the Substrate • pressure gradient • Solution: Insertion of a small hole in substrate prior to milling

  6. Obtaining A Uniform Coating • Ring Formation • Uniformly coated substrate

  7. Atomic Force Microscopy:Uniform Cr coating on Steel

  8. Atomic Force Microscopy: Non-uniformity of the Cr-on-steel Sample

  9. Effect of Mass of Cr Powder on Steel Substrate

  10. Milling Time: Effects on Surface Morphology

  11. Heat Treatment

  12. Further Investigations: Cr Coating on Al substrate • Studied: Powder mass in relationship to microhardness • Displayed increase in microhardness with increase in powder mass • Produced same characteristic curve as steel substrate • Atomic Force Microscopy also showed increases in surface morphology with increased powder mass

  13. Physical Properties of the Coating Powder

  14. Anomaly: Cu Coating on Al Substrate • No noticeable coating obtained under equivalent reaction conditions • Alcohol, Acetone, Silicon oxide were used in an effort to stimulate reaction • Copper coating obtained by shortening of milling time to 2 minutes

  15. Conclusion

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