Improving the cutting edge
Tiny tools — small enough to poke an individual lens on a ladybug’s eye — are getting more durable, thanks to ultrathin nanocrystalline diamond coatings developed by materials science graduate Patrick Heaney (MS ‘07, PhD ‘09) and his new company, NCD Technologies.
Heaney is refining techniques he developed and patented as a graduate student to enhance the performance of micro-cutting tools that one day could be used to shape ever-shrinking components employed across all industries.
Currently, tools made on this tiny scale break almost immediately unless given a protective coating. Diamond is the protective coating of choice.
“Diamond is my real goal and my real passion,” Heaney says. “I guess since I was a kid I always joked that I wanted to come up with a material better than plastic that was universally used. I really think diamond has that potential. Diamond is good because it has the lowest coefficient of friction and the highest hardness. It also has extremely high thermal conductivity and if you dope it right, it has electrical conductivity. So it really could be used in all of the nano- and microelectromechanical systems and in everyday devices like our phones and computers, cars and appliances.”
But getting diamond to stick to a tool without changing the tool’s shape is extremely challenging. Working in the lab of Mechanical Engineering Associate Professor Frank Pfefferkorn and former Engineering Physics Associate Professor Rob Carpick, Heaney developed a method of hot-filament chemical vapor deposition that not only reduces the coating thickness but also improves its adhesion.
In chemical vapor deposition, a tool is placed in a methane-filled chamber with a small amount of hydrogen. The gas flows over a hot filament. At the proper temperature and pressure, the carbon from the methane forms and grows on the tool as diamond.
“One of the problems with most tooling is that the substrate material is tungsten carbide, which is a very brittle material. Cobalt is added to improve the ductility and make the tools last longer, but that cobalt negatively affects the diamond growth,” Heaney says. “So you have to come up with some strategy to get rid of the effects of cobalt to allow you to grow diamond.”
The standard technique that allows diamond to grow involves first etching the substrate, but etching weakens the substrate before the diamond coating can be applied. Heaney found a way to apply diamond without etching, thereby improving the strength.
With a $150,000 Small Business Innovation Research grant from the National Science Foundation, Heaney is working with Janesville-based Performance Microtools to test his process. His company can apply coatings as thin as 50 nanometers to cutting tools — whereas the industry standard is between 2 and 10 microns. That’s an important difference when dealing with a cutting-edge radius as small as 1 micron.
Heaney says applying a 2-micron coating to such a small tool would blunt its sharpness and ruin its effectiveness. “With a diamond coating you see almost no burring. You get a very predictable clean surface finish, and the forces required to machine are reduced by as much as a factor of 10. That allows us then to increase the machining speeds by a factor of 10. So you can significantly decrease the machining costs,” he says.
After testing is completed, Performance Microtools could become NCD’s first customer. Based on the results of tests, Heaney hopes to move off campus and into his own commercial production lab, a goal that received a boost in summer 2010 when he finished in third place in the advanced manufacturing category of the Wisconsin Governor’s Business Plan Competition.
NCD could start selling coatings as early as spring of 2011. “But I’ll always stay tied to the university and Frank Pfefferkorn, hopefully to develop some new techniques that we’re thinking of and to see if we can make any significant improvements on the coating process,” says Heaney.
Heaney is no stranger to the research and development process. Growing up in Neenah, Wisconsin, he gained a lot of experience working for his father’s engineering firm. One of the projects he worked on there resulted in a patent for splicing Lycra as it is dispensed in diaper machines. He worked extensively with DuPont, Procter and Gamble, Kimberly Clark and major diaper manufacturers to make his process work better for those companies.
After earning a degree in physics and mathematics from Colgate University in New York, he returned to his father’s firm and worked on what he calls “random engineering.”
“I worked on a variety of machines,” Heaney says. “One machine made tinsel, another made heavy luggage tags at the airport. After a few years of that, I decided it was time to go back to school and get a PhD.”
Heaney looked at many programs, but with a math and physics degree from a liberal arts college, he found some were not taking him seriously. Most programs required him to take an additional year to 18 months of prerequisites before being admitted to the program. The UW-Madison Materials Science Program caught his eye because it requires students to take courses from more than one department.
“I really liked the feel of that,” Heaney says. “I liked the idea of collaborating with a lot of people. I’ve always been excited about engineering and taking lots of different ideas and merging them together to come up with the best solution. I thought that was really the strength of the program at Wisconsin and I was excited to move back to Wisconsin as well as get one of the better educations that I could find as I was exploring different PhD options.”
Now, with his doctorate in hand, Heaney is focused on developing new diamond coating technologies and new markets for the coatings. Beyond coatings for machine tools and parts, he sees potential in medical applications where non-biocompatible parts are coated with diamond and used in the body. Because current diamond-coating techniques result in premature delamination, diamond is not used in medical applications. But Heaney and Pfefferkorn have developed a new step to greatly improve adhesion, which could open the doors to myriad applications.
“Really, what it comes down to is that you could make a part out of anything you wanted and then coat it with diamond,” says Heaney. “It would be a superior part because it doesn’t matter what is on the inside, as long as you have great properties on the outside.”