Surface modification of 316L stainless steel with high-intensity pulsed ion beams

The surface of 316L stainless steel was irradiated by high-intensity pulsed ion beams (HIPIB) at ion current density of 100, 200 and 300 A/cm2 with 10 shots. The surface morphology and the phase structure in the near surface region of original and treated samples were analyzed with scanning electron microscope (SEM) and X-ray diffraction (XRD). Electron probe microanalysis (EPMA) was used to study the distribution of elements on the irradiated surfaces. It is found that the HIPIB irradiation can smooth the surface of the targets, and a preferred orientation presents in the surface layer of the treated samples. Otherwise, selective ablation of impurities occurs during the interaction between HIPIB and the targets. Due to the compress stress wave induced by the bombardment, the microhardness is increased significantly in a depth range of up to 200 μm, which reduces the friction coefficient of the treated surfaces and improves the wear resistance of them. Because the grain size reduces and the impurities content decreases in the irradiated surface layer, the electrochemical corrosion resistance is enhanced. In addition, HIPIB irradiation prolongates the fatigue life of 316L at room temperature due to a combination of the smooth surface and the high dislocation density in the surface layer of the treated samples.