FORMATION OF Ti–Cu INTERMETALLIC COATINGS ON COPPER SUBSTRATE

Abstract

In an attempt to modify the surface properties of copper substrate, Ti–Cu intermetallic compounds were produced on oxygen-free high-conductivity (OFHC) copper by physical vapor deposition followed subsequently with diffusion annealing. The structure and phase identification were evaluated by means of X-ray diffraction, electron probe microanalysis (EPMA), metallographic examination (optical and scanning electron microscopy [SEM]), energy-dispersive X-ray analysis (EDS), and microhardness measurements. Microstructural examination revealed that the compound coating consisted of three successive layers: the outermost layer (including the transformation product of β phase formed at diffusion temperature) contains α-Ti and Ti₂Cu, the intermediate layer consists of TiCu₄, and the innermost layer is a solid solution of copper in titanium. Ti–Cu intermetallic coatings significantly improved the hardness of the coated surfaces. The microhardness in the intermetallic layer was about seven times and the Ti–Cu solid solution was about three times more than that of the copper substrate.

Keywords:

• Coatings
• Compositional gradient
• Copper
• Diffusion annealing
• Diffusion coatings
• Hardness gradient
• Inward diffusion
• Physical vapor deposition
• Ti–Cu intermetallic compounds
• Ti–Cu phase diagram
• Titanium
• Titanium oxides

6.0 ACKNOWLEDGMENTS

The authors gratefully acknowledge the contributions of material science departments of Iran University of Science & Technology, Isfahan University of Technology, and the Mining & Metallurgical Department of McGill University in the performance of the experimental work.