The effect of crater creation on the fatigue strength and corrosion resistance of steels and titanium alloys irradiated by high-power pulsed ion beams

The effect of high-power pulsed ion-beam (HPPIB) irradiation and various methods of the surface treatment on the crater creation phenomenon (cratering) was examined with the use of Auger electron spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. The crater distribution density, sizes and shape, along with the microhardness and chemical composition inside and outside them were determined. It was shown that cratering on the surface of refractory alloys is due to the cathode material erosion and the nonstability in the physical and chemical state of the irradiated targets. The samples were treated with HPPIB. The irradiated samples were subjected to fatigue and corrosion tests. It was established that cratering leads to catastrophic fracture of the irradiated targets under the cycle load. For example, as a result of crater creation, the fatigue strength of VT18U alloy was decreased from 380 to 240 MPa. In this case the nucleation of fracture lies near the craters. Furthermore, the titanium alloys irradiated by HPPIB are subjected to pitting corrosion in seawater. It was shown that according to the test results, adjacent and dent-shape craters are the most dangerous defects under the cycle load.