Ion implantation effects on surface-mechanical properties of metals and polymers

The present work was undertaken to study ion implantation effects on surface-sensitive mechanical properties of metals and polymers. Fatigue properties of eight complex (E-series) alloys based on the composition Fe-13Cr-15Ni-2Mo-2Mn-0.2Ti-0.8Si-0.06C (E1) and single crystal Fe-15Cr-15Ni specimens, implanted with 400 keV B{dollar}sp+{dollar} and 550 keV N{dollar}sp+{dollar} to a total dose of 2.3 {dollar}times{dollar} 10{dollar}sp{lcub}16{rcub}{dollar} ions/cm{dollar}sp2{dollar} were examined. High temperature (600{dollar}spcirc{dollar}C) creep properties of {dollar}rm Bsp+/Nsp+{dollar}-implanted and 1 MeV Ar{dollar}sp+{dollar} implanted complex (E1) alloy and ternary Fe-13Cr-15Ni (B1) alloy were also investigated.; The dual implantation increased hardness but decreased fatigue life of the eight complex alloys. This was attributed to a shift from slip band crack initiation to grain boundary cracking. The existence of an optimum strengthening level was determined above which crack initiation occurred at grain boundaries rather than at slips bands. Similarly, evidence was provided for the shift to grain boundary cracking for four simple Fe-13Cr-15Ni alloys. The single-crystal specimens also showed a reduced fatigue life after implantation due to concentration of slip along intense slip bands. High temperature creep properties of the E1 and B1 specimens were significantly improved after {dollar}rm Bsp+/Nsp+{dollar}-implantation and an increase in the time to rupture by over 70% was found. Examination of the failed specimens showed that all specimens failed by intergranular fracture and ion implantation delayed intergranular void nucleation and crack initiation. This was the first effort to study multiple-ion-implantation effects on creep properties of alloys. The Ar{dollar}sp+{dollar}-implantation increased creep life of the B1 alloy but decreased life for the E1 alloy. This was attributed to competing effects of Ar{dollar}sp+{dollar}-bubble formation at grain boundaries and strengthening of matrix by bubbles as well as irradiation damage effects.; Four polymers, polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyethersulfone (PES) were implanted with 200 keV B{dollar}sp+{dollar} to three different doses. PS was also implanted with 100 keV B{dollar}sp+{dollar} ions and with 200, 500 and 1000 keV Ar{dollar}sp+{dollar} ions to three doses to study energy and ion-species dependence. Near-surface hardness changes were investigated using a nanoindentation technique. The B{dollar}sp+{dollar}-implanted polymers were also investigated for effects on tribological properties. The near-surface hardness of all the ion-implanted polymers increased with dose and energy. Implantation effects were found to be sensitive to the structure of the polymer. The hardness changes were explained in terms of cross-linking and the deleterious effects of chain-scission. Microstructural correlations were also obtained. Good improvements were obtained for wear properties though there was again a sensitive dependence on dose. An optimum dose was found at which minimal wear was observed. No specific correlations were made between friction coefficient, hardness and wear resistance.