Ultrasonic nanocrystal floor modification restores chrome steel’s corrosion resistance

Present in every little thing from kitchen home equipment to sustainable power infrastructure, stainless steels are used extensively as a consequence of their glorious corrosion (rusting) resistance. They’re an necessary materials in lots of industries, together with manufacturing, transportation, oil and fuel, 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 trade.”

Sridharan and Kasturi Narasimha Sasidhar, an assistant scientist in Sridharan’s group, have demonstrated a brand new method for restoring chrome steel’s corrosion resistance that could possibly be a lot quicker and doubtlessly cheaper than standard high-heat remediation strategies.

To basically perceive why their method 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 revealed March 5, 2025, within the journal Metallurgical and Supplies Transactions.

For his or her method, 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 therapy, which is a extremely large deal,” Sridharan says.

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

After all, the researchers wished to grasp why their method was efficient. Conventional microscopy strategies like scanning or transmission electron microscopy alone have been inadequate to yield the info essential to reply their questions.

“CAMECA’s atom probe tomography expertise allowed the researchers to take 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 functions scientist at CAMECA Devices Inc.

Chrome steel comprises 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 chargeable for the drastic loss in corrosion resistance.

The staff found that the ultrasonic nanocrystal floor modification therapy 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 functions and enterprise developer at CAMECA and a co-author on the paper, who labored carefully 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.”