Evidence of scuffing initiation by adiabatic shear instability

A mechanism for the initiation of scuffing based on adiabatic shear instability was assessed experimentally through the measurement of dislocation densities by X-ray diffraction. Scuffing was predicted to occur when the rate of local thermal softening exceeded that of work hardening in the tribological contact. Since these rates were dependent on microstructure, the theory was tested by performing scuffing tests on SAE 4340 steel subjected to five different heat treatments. The scuffing resistances were consistent with the theory, and thermal events during the tests and the resulting microstructural morphologies were consistent with a locally adiabatic environment. The dislocation densities measured in samples from tests stopped before, during, and after scuffing were consistent with the theory. Use of the Advanced Photon Source (APS) at Argonne National Laboratory was supported by the U.S. Department of Energy under Contract W-31-109-ENG-38.