Norton asphalt reclamation carbide-tip braze joint

Asphalt-reclamation tooling: traditional tungsten carbide tip replaced with brazed sintered-diamond tip for longer life. Roughly 1 cm of sintered diamond brazed to a steel body; survives high-impact road grinding.

[Tom passes a brazed diamond-tip asphalt tool around.] Here's a brazing example. This is part of a tip for reclaiming asphalt from the street. You may have seen them late at night on the highway — a great big machine with a bunch of these tips going around in circles, beating up the asphalt so they can resurface the road. The tip is usually made out of tungsten carbide, which is one of the hardest materials we know, but you can get a much better life if you use sintered diamond. The black stuff there, about a centimeter across, is sintered diamond. It has to be brazed. So you have to learn how to braze it so it doesn't fail as it beats up the road to reclaim the asphalt.

Tom's student developed an in-situ composite braze alloy (Cu-Sn-TiH2-C) for brazing carbide bits to highway asphalt-reclamation tooling. Titanium hydride decomposes in vacuum brazing, releasing Ti metal which reacts with C to form TiC particles in the joint. Result: braze alloy CTE halved vs. Cu-base; tool life tripled in field test on actual road surfaces. Failure mode addressed: tip loss during overnight road work stopping the whole reclamation machine.