398093 Deformation and Bonding of Cold Sprayed Iron-Based Amorphous Metal Particles
Name: Maryvivian Okwara
Year: Class of 2016
Faculty Mentor: Professor Constance Ziemian (Mechanical Engineering department)
Deformation and Bonding of Cold Sprayed Iron-Based Amorphous Metal Particles
To date, various attempts have been made to produce amorphous iron (Fe)-based metallic coatings using conventional deposition methods such as thermal spray techniques. These methods, however, have been shown to compromise the amorphous structure of the coatings and adversely affect the superior properties of the metallic glass, such as corrosion and wear resistance. The overarching goal of this project is to determine the feasibility of depositing fully amorphous coatings using a unique, kinetic energy-based process known as the cold spray. The project specifically tests the hypothesis that cold-sprayed Fe48Cr15Mo14C15B6Y2 at.% (SAM1651) metallic glass particles will sufficiently deform and bond to a mild steel substrate with the proper optimization of process parameters. This is accomplished by analyzing the deformation and adhesion of individual Fe-based metallic glass particle impacted upon a steel substrate, known as cold spray splat tests. Several splat tests were completed with a variety of gas temperatures (850°C, 900°C, 950°C, 975°C, 1000°C), gas pressures (3MPa, 4MPa), powder feed rates (0.2rpm, 0.25rpm, 1 rpm), and spray raster speeds (1200mm/s, 2400mm/s, 3600mm/s). The resulting specimens were gold-coated and analyzed using scanning electron microscopy (SEM). The deformed particle morphologies were found to vary as a function of primarily gas temperature, ranging from well-deformed to un-deformed. SEM analysis also indicated that a significant percentage of the impacted particles rebounded off of the steel surface and left craters in the substrate. These craters inspired further research focused on the empirical determination of the critical velocity required for particle adhesion. Although this type of study has been done for cold-sprayed crystalline metals, the cold-spray critical adhesion velocity had not been previously defined for amorphous metals. Material strength and stiffness needed for the critical velocity analysis were determined using nanoindentation. This empirical modeling work is ongoing, and results are expected to define a window of gas temperatures and pressures for the successful cold-spray deposition of Fe-base metallic glass particles.
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