Tantaline (Lyngby, Demnark; http://www.tantaline.com; Booth 645) has developed a process that creates a surface alloy of tantalum on a metal substrate (typically stainless steel). As a result, the surface acquires the corrosion resistance of tantalum — the most corrosion resistant metal commercially available — without having to fabricate complicated parts from the expensive metal. Unlike alternative coating methods that are sprayed or dipped, Tantaline’s Alloy Bonding Surface Technology causes tantalum atoms to grow into the substrate, creating an alloy at the interface. As a result, the surface alloy cannot chip or spall, resists pressure variations, and has a wear-resistance similar to or better than stainless steel, says Søren Eriksen, Tantaline’s R&D manager.
Parts to be treated are first placed into a vacuum chamber where a mixture of tantalum pentachloride and hydrogen reacts at 700–900°C and 15–50 mbar to form a dense film of tantalum metal on the surface by chemical vapor deposition (CVD). Because the feed gases are distributed by convection and diffusion, the CVD process is nearly independent of the part’s geometry, enabling even complex parts to be treated. The tantalum layer is then alloyed with the core metal by a patented alloy bonding technology, and then a layer of pure tantalum is grown on the surface alloy, giving the final surface all the characteristics of pure tantalum. A tantalum thickness of 50 µm is sufficient for most applications, but can be as large as 200 µm if needed, says Eriksen.
For the past 15 years, the company has been researching, developing and producing a variety of valves, fittings, instrumentation and other components for customers who deal with corrosive processing environments (such as sulfuric and hydrochloric acid). Earlier this year, Tantaline started up a new facility, which increased its capacity by ten times. Treated parts are expected to be directly competitive with those made of special metals, such as titanium, zirconium and nickel alloys, says Eriksen.
Gerald Ondrey