EFFECT OF A THERMOCHEMICAL TREATMENT ON THE FATIGUE-STRENGTH OF CONSTRUCTIONAL STEELS

Fatigue characteristics in the form of Smith diagrams are reported for both a steel containing 0. 18 per cent of carbon, 1. 01 per cent of manganese and 0. 08 per cent of titanium after case hardening and carbonitriding, and for a steel containing 0. 33 per cent of carbon, 0. 43 per cent of manganese, 0. 24 cent of chromium and 0. 28 per cent of vanadium after nitriding. The character of fatigue fractures of structural alloy steels after case hardening, carbonitriding and nitriding is described as a function of the surface layer and based on fractographic tests. The advantages of a thermochemical treatment are demonstrated.