Harder or Tougher? One common fear is that cryogenic treatment increases the tool’s hardness, which equates to brittleness. Not so, according to Bond.

“This process doesn’t make tooling harder,” Bond said. “In fact, some customers request that I raise the tool’s hardness, but I have to turn them away.” Because the process converts just the retained austenite to martensite, it transforms a maximum of 17 percent of the material. The hardness increases about the same amount, which equates to just 1 or 2 points on the Rockwell hardness scale,Bond said.

That said, misunderstandings are common.

“Many people equate this with a physics experiment,” Paulin said. “If you dip a flower into liquid nitrogen, it will freeze instantly, and it will be so brittle that a slight impact will cause it to shatter. People also confuse it with dropping an ice cube into a cup of coffee, which causes the ice cube to crack or split. That’s due to differential heating,” he said, describing a process thatapplies too much heat too suddenly. “We do the opposite of that. We cool the surface and the core, but slowly, keeping them in equilibrium. It imparts uniform residual stresses at the surface,” he said, resulting in a more durable tool.

The misconceptions aren’t unfounded, Paulin explained.

“Untempered martensite is very hard, and very brittle,” Paulin continued. “Subsequent draws at elevated temperatures for the right amount of time temper the material, imparting a toughness that increases its durability.”