Rolling contact fatigue of three pearlitic rail steels

Abstract

The effects of varying contact pressure and creepage on the early stages of rolling contact fatigue in three pearlitic rail steels have been investigated in the laboratory under water lubricated conditions. In the test machine used, a non-contacting eddy current probe detected very small fatigue cracks and was used to stop tests before spalling could destroy the fatigue initiation sites in order that the metallography of crack initiation could be undertaken. Crack morphologies similar to those found in wheel-rail contact have been observed. Except at the highest creepages and contact stress used, there was little evidence that manganese sulphide inclusions contributed to crack initiation. In contrast, hard oxide inclusions did contribute to initiation. The head-hardened grade eutectoid steel had the best resistance to rolling contact fatigue. The naturally hard eutectoid steel was the next best, whilst the lowest strength steel gave the worst performance. Crack networks were formed in the specimens tested at nominal contact stresses of 1200 MPa and 1500 MPa. Isolated cracks were produced in the specimens tested at 1800 MPa.