Surface Strengthening Mechanisms of Ion-Implanted Layers

Ion implantation is a well known method to modify the properties of the material surfaces, such as mechanical properties, wear resistance, electronic properties, erosion resistance and biological compatibility. In the industry, this technology is mostly used to enhance the mechanical properties of the components. The improvements of the mechanical properties are 1 usually attributed to the formation of new strengthening phases, solution strengthening, dislocation strengthening, grain refinement, etc. As far as we know, there are very few direct evidences to reveal the individual roles of these factors during modification. In the analysis of the nanohardness of soft materials, the decrease of the hardness with increasing loads is generally simply regarded as the result of combination of hard film and soft substrate. The mechanical properties strengthening by radiation damage are usually typically underestimated.
In this study, we choose 321 austenitic stainless steel as the substrates and implant them with N and by Ti to investigate in the strengthening mechanism of the mechanical properties. A nano-indenter is used to measure the hardnesses under various loadings. The N-modified and Ti-modified layers on the same substrates behave differently in the hardness (MPa) vs loading (mN) diagram. The effects of radiation damage and the strengthening phase are analyzed. Characterization of the modified layers is conducted using Auger electron spectroscopy (AES), small angle X-ray diffraction (GIXRD)), and other analytical techniques.