Failure Analysis on the GCr15 Bearing Steel and the 20CrMo Carburized Steel Nuts of the Ball Screw Pair

Abstract

Failure analysis on the GCr15 bearing steel and the 20CrMo carburized steel nuts was performed after two sets of fatigue tests of GD8020×1100 ball screw pair. By means of scanning electron microscopy observation, energy dispersive analysis and microhardness testing, it is found that there is an obvious indentation, slight pitting and microcracks on the raceway of the GCr15 bearing steel nut and shows the characteristics of contact fatigue failure. The nonuniformity of microstructure and the lower carbon and chromium content in the indentation, leading to local lower hardness, account for the nut failure. While the raceway of the 20CrMo carburized steel nut is more rough with scratches caused by the damaged steel balls so as to show the characteristics of wear failure. Therefore there are different failure ways for the different nuts made by different steels and heat treatments under the same fatigue testing condition.