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PLANT

Sigmabond explodes cladding parameters


September 10, 2008
by Plant Staff

Sigmabond president Harry Sildva and Vahid Safavi, a University of Toronto researcher, look over some testing at the ultraasmic bondstructive lab.

Photo: Rodney Daw

Tucked away in a sandpit near North Bay, Ont., Sigmabond Technologies Corp. has been tinkering with a new technology that promises to revolutionize the way clad metals are made. Potential applications are as diverse as bone implants, heat exchangers, electrical transition joints, armour plating and metal cladding.

The common element among them is the way materials are bonded using patented advancements in explosive bonding. Sigmabond’s technical team, guided by Roy Hardwick, vice-president of technology and an expert in explosive bonding, has developed a new process that raises the bar for cladding titanium to steel.

Seven years ago, a “technology partnership” was initiated between Harvey Pellegrini, network liaison manager at the Ontario Centres of Excellence (OCE), Dr. Tony Sinclair, professor and chair of the Department of Mechanical and Industrial Engineering at the University of Toronto and Sigmabond. It all started with a meeting of the minds that took place during an OCE Partnerships Trade Show, an annual event that brings academic and commercial pioneers together to further the commercial application of science and technology.

“We were interested in what each other did but it was too early to say, ‘Yes this is clearly worth a zillion dollars,’” says Sinclair.

OCE got the ball rolling with an Interact Grant, which initiates new collaborative research partnerships between industry and academe.

“[The grant was] fairly small, about $15,000, but it was enough to make the interaction worthwhile and for us to do some initial work together,” says Sinclair.

Pellegrini secured the approvals within a week, so Sinclair got some students involved with Sigmabond’s team and they went to work. Within a few months, research had established a link between bonding parameters, morphology and strength in the making of copper and aluminum samples. From that knowledge, refinements in the technology were developed that would result in a new generation of aluminum clad copper and copper heat exchangers.

“Sigmabond had already acquired a fair bit of field experience making these bonds and they were trying to optimize their parameters,” says Sinclair. A team of students, using state-of-the-art facilities, were able to examine the bond interface in samples provided by Sigmabond and identify areas of weak or no bonding.

“Our lab has tools, primarily having to do with ultrasonics [a type of testing that uses sound waves to look inside metals], where we are able to inspect inside the weld,” says Sinclair. “Harry Sildva, Sigmabond’s president, was quite amused when I told him, ‘I don’t want just good welds, I want really crummy ones as well so I can see the difference between them.’”

One of the products Sigmabond introduced to the lab was an advanced new steel plate covered with a layer of titanium, called titanium clad.

These two metals are among the most difficult to bond. They’re used in the fabrication of industrial equipment such as pressure vessels for the energy industry. Solid steel can’t be used because it’s not sufficiently resistant to corrosion and solid titanium is too expensive. Since titanium is so resistant to corrosion, applying a thin veneer clad to the steel produces a material that’s as strong as steel, but corrosion resistant. The only way to make such a material is explosive bonding.