Infrared heat treatment of Ti-6Al-4V with electroplated Cu
The objective of this study is to investigate an innovative infrared (IR) technique to enhance adhesion of electroplated copper (Cu) on Ti-6Al-4V without dichromate dipping. The ultimate goal is to develop a Cu coating process on Ti-6Al-4V without hazardous hexavalent chromium (Cr) solution treatments. Cu coatings of around 50 µm were electroplated on Ti-6Al-4V specimens at a current density of 0.03 A/cm2 in an acidic Cu solution. To improve adhesion of coatings, IR heat treatments were performed on the Cu-coated samples at different temperatures and durations: 860 °C for 600 s and 875 °C for 20–120 s. This process was accomplished in an attempt to replace the use of dichromate dipping before electroplating. For samples heat treated at 860 °C, no bonding existed, even after 600 s. It is believed that solid-state diffusion prevailed at 860 °C and that 600 s was not enough for sufficient diffusion to occur. Adhesion was poor when samples were heat treated at 875 °C for 20 s. Excellent adhesion was observed when the heat treatment holding time was increased to 40 s. For 90 s, the surface appearance of coatings partially changed from Cu-colored to a grayish color. There was no Cu left on the surface after a 120 s heat treatment. From optical microscopic observations on sample cross sections, an interlayer between the Cu and Ti-6Al-4V formed when heat treated at 875 °C for 40 s and longer. The interlayer thickness increased as the holding time increased, until depletion of Cu. The sheet resistivity of coated specimens was on the order of pure Cu for samples heat treated at 875 °C and less than 90 s. During the 875 °C heat treatment, the following occurred: solid-state diffusion of Cu in Ti-6Al-4V, formation of eutectic solutions, dissolution of Cu and Ti-6Al-4V into the liquid phase, and the formation of intermetallic compounds. The lowest eutectic temperature of 875 °C played a key role in this innovative process of Cu coating on Ti-6Al-4V.
Keywordsinfrared processing intermetallic compounds sheet resistivity Ti-6Al-4V
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- 1.R.R. Boyer: “An Overview on the Use of Titanium in the Aerospace Industry,” Mater. Sci. Eng., 1996, A213, pp. 103–14.Google Scholar
- 2.C.G. John: “Electroplated Coating of Titanium for Engineering Applications,” in Proceedings International Conference, Designing with Titanium, Institute of Metals, London, UK, 1986, pp. 160–65.Google Scholar
- 3.M. Thomas, “Plating on Titanium,” Plat. Surf. Finish., May 1983, pp. 96–98.Google Scholar
- 5.A. Bloyce, P.H. Morton, and T. Bell: “Surface Engineering of Titanium and Titanium Alloys,” ASM Handbook Vol. 5, Surface Engineering, ASM International, Materials Park, OH, 1994, pp. 845–66.Google Scholar
- 6.D.H. Wilson: Surface Cleaning, Finishing, and Coating, Vol. 5, Metals Handbook, 9th ed., American Society for Metals, Metals ParK, OH, 1982, pp. 650–68.Google Scholar
- 7.J.L. Murray: Phase Diagrams of Binary Titanium Alloys, ASM International, Materials Park, OH, 1987.Google Scholar
- 8.J.H. Li and R.Y. Lin: Infrared Heat Treatment of Copper Coated Ti-6Al-4V, ASM International, Surface Modification, Materials Park, OH, 2002.Google Scholar
- 9.C.J. Smithells: Metals Reference Book, ASM International, Materials Park, OH, 1992.Google Scholar