Subsurface damage development during fretting fatigue of high strength steel

The results of fretting fatigue experiments performed on two high-strength structural steels, PH 13-8 Mo stainless steel and quenched and tempered 4340 steel, are evaluated. Observations regarding the subsurface deformation and cracking behavior of the steels are compared and contrasted. It was found that the fretting stresses influenced early crack growth to a greater depth in PH 13-8 Mo stainless steel than in 4340 steel. In addition, experiments on PH 13-8 Mo led to the development of a region below the fretting scar that underwent a microstructural transformation, while experiments on 4340 steel did not. Likely reasons for this discrepancy are suggested. Differences in the formation of oxide layers and the occurrence of adhesion between the two materials are also discussed.