The effects of oil-quenching and over-tempering heat treatments on the dry sliding wear behaviours of 25CrMo4 steel

This study, it was aimed to examine the dry sliding wear properties of the tempering and over-tempering heat treatments of 25CrMo4 steel, which is used in the manufacture of parts such as axle shafts, axle sleeves, turbine parts, and turbine blades in the automotive industry Oil-quenched 25CrMo4 steels could be subjected to high temperatures where they are used and may undergo over-tempering period. In this case, there may be changes in many mechanical properties such as wear. For this purpose, microstructural examination, hardness, and dry sliding wear tests were performed on the materials. As a result of the tests, it was observed that the sample, on which we applied the tempering and over-tempering heat treatment, had a martensitic microstructure. The hardness values of the tempered and over-tempered samples increased compared to the raw material and as expected, partially decreased in the over-tempered sample. Dry sliding wear losses decreased significantly in oil-quenched and over-tempered samples compared to the raw material. Even though the hardness decreased in the over-tempered sample, the wear loss was low. The variation between wear losses increased further with the increase in friction forces. While the maximum friction coefficient was highest in the oil-quenched sample, it was lowest in the raw sample.