Abstract
The physicochemical state of the surface layers of specimens of alloy VT18U subjected to ion-beam (B+, N+, C+, Pd+, La+) and heat treatment is determined by methods of electron-Auger spectroscopy, X-ray structural analysis, exoelectron emission, and Faraday impedance. It is shown that the thickness of the ion-alloyed layer does not exceed 1 μm. Tests are carried out for specimens in the original and irradiated conditions for cyclic endurance at 500°C whose results indicate that it may be possible to increase their life by several factors by means of ion-beam treatment. Fracture surfaces are studied by electron fractography. It is established that the effectiveness of ion-alloying from the point of view of improving fatigue resistance is due to a combination of chemical and physical processes which occur in the thin surface layer with irradiation and heat treatment as a result of which there is a change in the mechanism of crack initiation (for ion-alloyed specimens the failure site is beneath the surface at a depth of 6.5–135 μm, and for original specimens it is at the surface).
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