A review of four-ball methods for the evaluation of lubricants

A review of four-ball wear tester and test methods developed at Penn State by Prof. Emeritus E.E. Klaus (Deceased) and students of Klaus. The test methods include standard methods for fluid and additive evaluation, microliter tests to evaluate tribochemical reactions in the contact zone, Ball-on-Three Flat tests to evaluate materials and fluids, scuffing test methods and sequential four-ball tests, one of which was developed to screen hydraulic fluids for full-scale pump stand tests and field vehicles Applications range from room temperature to over 425°C. The variety of methods demonstrate the versatility of the FBWT, including applications related to the tribology of hydraulic fluid systems.