Adhesion Strength of Cordierite Bulk Coatings on Molybdenum Substrates

Cordierite was adhered to molybdenum using various metallic interlayers of copper, nickel, and chromium. The development of a coating adhesion test methodology was required to choose between interface designs. An indentation method was chosen because of ease in testing and availability of fracture mechanics interpretations of test data. The interfacial fracture toughness was determined from indentation load vs. crack length data by examining the residual stress and critical buckling load of the ceramic coatings. The interfacial fracture toughness values obtained using a slightly different indentation analysis agree with those in the literature. Quantitative chemical analysis of the interface microstructure was used to explain differences in interfacial fracture toughness values for samples with different metallic interlayer designs. The best interface design for adhering cordierite glass-ceramic coatings to molybdenum was found to be molybdenum / 2 μm copper / 4 μm chromium / cordierite. Dedication This paper is dedicated to my parents, who taught me how to think, live, love, and learn. Acknowledgments Above all, I thank my committee for their utmost patience and understanding. I would also like to thank all the graduate students, professors, and other experts for their help along the way: Jesus Calata, Dr. Allan Ward, Michael and Rebecca Stawovy, Judson Marte, Dr. Gang Chen, Marshall “Mac” Maccord, Dr. Eric Pappas, and Todd Solberg...thanks.