The dry wear of steels I. The general pattern of behaviour

The broad trends of the wear rate when steels rub together without lubrication have been studied by means of pin and ring apparatus. Over a wide range of load (10 g to 40 Kg) and sliding speed (1$\cdot $7 to 266 cm/s) the wear process at equilibrium is either of a severe type, producing coarse metallic debris, or of a mild type, producing fine oxidized debris. The corresponding wear rates differ by more than two orders of magnitude. Transitions from one wear process to the other occur at well-defined loads and for soft steels a basic pattern, comprising three transitions, has been identified: T$_{1}$, a change from mild wear to severe at light loads; T$_{2}$, a change from severe wear back to mild at higher loads; T$_{3}$, a minor change in the mild wear rate at loads above T$_{2}$, characterized by divergent wear rates of the pin and ring. The way in which this pattern varies with the sliding speed and with the composition and hardness of the steel is traced and the findings of previous investigations co-ordinated in the general framework.