Ultrasonic nanocrystal floor modification restores chrome steel’s corrosion resistance

Present in every thing from kitchen home equipment to sustainable power infrastructure, stainless steels are used extensively attributable to their wonderful corrosion (rusting) resistance. They’re an essential materials in lots of industries, together with manufacturing, transportation, oil and gasoline, nuclear energy and chemical processing.

Nonetheless, stainless steels can endure a course of known as sensitization when subjected to a sure vary of excessive temperatures—like throughout welding—and this considerably deteriorates their corrosion resistance. Left unchecked, corrosion can result in cracking and structural failure.

“It is a main drawback for stainless steels,” says Kumar Sridharan, a professor of nuclear engineering and engineering physics and supplies science and engineering on the College of Wisconsin–Madison. “When chrome steel will get corroded, parts should be changed or remediated. That is an costly course of and causes prolonged downtime in business.”

Sridharan and Kasturi Narasimha Sasidhar, an assistant scientist in Sridharan’s group, have demonstrated a brand new strategy for restoring chrome steel’s corrosion resistance that may very well be a lot sooner and doubtlessly cheaper than typical high-heat remediation strategies.

To essentially perceive why their strategy was so profitable at restoring corrosion resistance, the researchers harnessed a sophisticated approach known as atom probe tomography in collaboration with Madison-based firm CAMECA Devices Inc. (AMETEK), which has ties to UW–Madison.

The staff detailed its findings in a paper printed March 5, 2025, within the journal Metallurgical and Supplies Transactions.

For his or her strategy, the researchers used a expertise known as “ultrasonic nanocrystal floor modification” on a pattern of sensitized chrome steel. On this course of, a tough pin faucets the metal’s floor at extraordinarily excessive frequencies.

“We confirmed that ultrasonic nanocrystal floor modification can restore the corrosion-resistant state of the chrome steel, while not having any warmth remedy, which is a very massive deal,” Sridharan says.

Whereas ultrasonic nanocrystal floor modification isn’t readily scalable, Sridharan says this analysis may open a door to related, extra scalable floor modification strategies to optimize the efficiency of stainless steels.

After all, the researchers needed to grasp why their strategy was efficient. Conventional microscopy methods like scanning or transmission electron microscopy alone have been inadequate to yield the information essential to reply their questions.

“CAMECA’s atom probe tomography expertise allowed the researchers to have a look at the metal on the nanometer scale, in three dimensions, and to exactly measure the placement of the weather within the materials,” says Sasidhar, now a senior purposes scientist at CAMECA Devices Inc.

Chrome steel incorporates about 18% chromium, which is what makes it corrosion resistant. As sensitization happens, chromium will get depleted in tiny areas within the chrome steel. Notably, these tiny areas of depletion are liable for the drastic loss in corrosion resistance.

The staff found that the ultrasonic nanocrystal floor modification remedy equalized the chromium focus within the tiny depleted areas, which restored the corrosion resistance.

Sridharan says UW–Madison’s connection to CAMECA, a world-leading producer of atom probe tomography tools, performed a key function on this breakthrough. The precursor to CAMECA’s atom probe tomography enterprise was Imago Scientific Devices Company, an organization based in 1998 by Tom Kelly, a former professor of supplies science and engineering at UW-Madison. In 2010, Imago was acquired by AMETEK and integrated into the CAMECA enterprise unit.

“The corporate has robust historic hyperlinks to UW–Madison,” says Robert Ulfig (BSNEEP ’94, MSMS&E ’97), senior purposes and enterprise developer at CAMECA and a co-author on the paper, who labored intently with Sridharan throughout his graduate research. “It is thrilling that we have been in a position to collaborate with the college to make this impactful discovery.”