July 3, 2009: Rushford Hypersonic LLC says it has applied its hypersonic plasma particle deposition (HPPD) coating process to its first “real-world” product: a drill bit that it says increased its lifetime by ~40×.
The company is utilizing technology developed at the U. of Minnesota, which hurls 2-20nm particles at Mach 8 speed; the force of impact causes a phase-change in the particle causes them to infiltrate and “stick” with a weld-like bond, vs. just coating the surface like other plasmaprocesses. The company claims the HPPD coating creates a super-hard (36-50GPa hardness rating) and fracture-tough (~6MPa) thin film carbide, and it also fills in holes and gaps left by other plasma processes.
High-resolution SEM photo of HPPD film. (Source: Rushford Hypersonic)
In the new tests, a 1/4-in. dia. jobber drill bit was coated with silicon carbide using the HPPD process, and dry-drilled through 1/2-in 304 stainless steel, with no cooling fluid or lubrication, for 238 holes, and then on 1-in. 304 stainless steel for another seven holes until finally faltering and failing due to shank fatigue. The same uncoated drill bit (out of the same lot) completed just six holes in the 1/2-in. stainless steel and failed on the 7th attempt.
Further testing will continue, but the company sees “an effortless transition” to applications including machine tools, mechanical parts, and implantable medical devices.