AUTHOR:
Frank Lemkey, Ph.D., UConn
Frank Lemkey, Ph.D. is C Visiting Professor of Metallurgy (UConn) with more than 40 years of experience in processing high temperature alloys and coatings produced by electron beam vapor deposition.
Phygen has developed and patented a magnetically enhanced cathodic arc process to deposit tough adherent micrograin CrN coatings that possess high hardness and wear resistance. Already successful in protecting and enhancing the life of ferrous tooling, these coatings also may find further application in protecting rotating titanium components of helicopter and gas turbine engines especially those operating in marine environments.
Phygen’s FortiPhy™ XVD surface coating, CrN coating offers excellent adherence to steel and improved fracture toughness. To achieve increased durability and performance in transmission components, thin diamond-like coatings have captured the fancy of major helicopter manufacturers for application on planetary and spur gears. Several failure modes derived from bending and sliding contact fatigue, such as coating chipping, subsurface cracking, and debonding, have hampered the general acceptance of this technology. Phygen’s FortiPhy XVD, with its demonstrated excellent adherence to steel and improved fracture toughness derived from a nanograin-sized (15-40nm) microstructure, promises a cheaper and better coating pathway. Together with a hardness of 67 to 80 percent of diamond and a dry coefficient of friction of about 0.20, FortiPhy XVD appears to be an excellent candidate to outperform DLC coatings on gears.
FortiPhy XVD also may provide greater smoothing of the surface asperities during ‘run in’ compared with DLC because of its lower intrinsic hardness and smoother surface roughness (40-70 nm). This stems from deposition by Phygen’s FortiPhy™ XVD process compared to a different coating manufacturer’s magnetron sputtering of WC/Ni targets in C2H2/Ar atmospheres. Improved gears and bearings in transmissions using thin adherent hard coatings promise 5- to 10-times the life, and improvements in overhaul periods. For certain military applications, longer ‘oil out’ operating periods experienced during combat situations is a valuable flight advantage of coated gears.