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
What is Ball Milling?
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
Key Variables Milling Time Number and Size of Milling Balls Powder Mass Powder Mass to Ball Ratio
Initial Experimental Problems Downward Curvature of the Substrate pressure gradient Solution: Insertion of a small hole in substrate prior to milling
Obtaining A Uniform Coating Ring Formation Uniformly coated substrate
Atomic Force Microscopy:Uniform Cr coating on Steel
Atomic Force Microscopy: Non- uniformity of the Cr-on-steel Sample
Effect of Mass of Cr Powder on Steel Substrate
Milling Time: Effects on Surface Morphology
Heat Treatment
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
Physical Properties of the Coating Powder
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
Conclusion