Use of multiple criteria to map the high-temperature scuffing behavior of Co-based superalloys

The goal of this work was to rank, as quantitatively as possible, the high-temperature scuffing characteristics of a series of Co-based materials, including coatings, for possible use in wear-critical components like those in diesel engine exhaust systems and emission-controls. A cylinder pivoting on its side against a flat tile was used as the testing geometry. All tests were performed at 600 °C in air. The time-dependent torque response was recorded for each 60 min test to investigate trends in friction as surfaces roughened and debris deposits built up. Candidate materials included Stellite 6B, Pleuco 33 (a white cast iron), nitrided stainless steel Type 310, IDM 5399 (a high-silicon, molybdenum iron), and coatings of both Tribaloy T-400 and Stellite 3 on stainless steel. Measurements of the damaged areas on the scuffed tiles were used to calculate a specific normal load and plot it versus the roughness of the worn tiles to map experimental results in a way that indicated the severity of scuffing for each material combination. Data on the map were annotated to reflect visual observations of the extent of damage as well. Using this test method and the foregoing criteria, nitrided type 310 stainless steel against T-400 gave the best overall performance.