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Abstract: Plasma-based low-energy nitrogen ion implantation, including plasma source ion nitriding/carburizing and plasma source low-energy ion enhanced deposition, has emerged as a low-temperature surface engineering technique for metal and alloy. In this paper, the pure metal Ti samples have been modified by the plasma source ion nitriding process at a process temperature of 700°C for a processing time of 4h. The nitrided Ti surfaces were constructed of a continuous and dense Ti2N compound layer about 2μm thick and a 7–8μm diffused layer. During tribological test on a ball on disk tribometer against the Si3N4 ceramic counterface, a low friction coefficient of about 0.3 and the faint wear volume were obtained for the nitrided Ti samples. The cyclic polarization curves of the nitrided Ti samples in 3.5% and 6.0% NaCl solutions showed that the improved pitting corrosion resistance with an increase of corrosion potential and a decrease of passive current, compared with that of the unnitrided Ti sample. The plasma source ion nitriding of the Ti samples provided the engineering surfaces for the functional applications with the combined improvement in wear and corrosion resistance. [Copyright &y& Elsevier]

Abstract: A high nitrogen face-centered-cubic phase (γN) was obtained on the nitrided surface of 1Cr18Ni9Ti austenitic stainless steel by plasma-based low-energy nitrogen ion implantation. No pitting corrosion for the γN phase was confirmed by electrochemical polarization measurement in 3% NaCl solution. The protective passive film with a duplex character, iron hydroxide/oxides in the outer region and chromium hydroxide/oxides and iron oxides accompanying chromium and iron nitrides in the inner region, was by 2–3 times thicker than that of original stainless steel. The thick iron hydroxide/oxides region formed on the chromium hydroxide/oxides region due to the increase of alkalinity in the solution, leading to barrier against penetration of localized attack of the aggressive ions. The equivalent general corrosion resistance for the γN phase was observed in 0.5 mol/l H2SO4 solution relative to the original stainless steel. The passive film formed on the γN phase in 0.5 mol/l H2SO4 solution was similar to that of original stainless steel. The different role of nitrogen was proposed in pitting corrosion resistance and general corrosion resistance of austenitic stainless steel. [Copyright &y& Elsevier]

Abstract: The high-intensity pulsed ion beam (HIPIB) technique has emerged as an efficient tool for surface engineering of materials. In this work, the Ti6Al4V alloy is irradiated by HIPIB at an accelerating pulse voltage of 300 kV in a pulse width of 75 ns (FWHM) with an ion current density ranging from 60 A/cm2 to 250 A/cm2 under one shot. The X-ray diffraction (XRD) analysis shows that the irradiated surface composed of α-Ti phase and β-Ti phase in minor amount retains the original structure of the Ti6Al4V alloy. The irradiated surfaces have an increased microhardness of about HV0.25 N 4.1 GPa in the modified layers 150–750 μm thick, which depend on the ion current density of 60–250 A/cm2. The wear tests are performed on a pin-on-disc tribometer in which the irradiated samples are rubbed against a hardened Cr12MoV high alloy steel disc (HRC 62–63) under a normal load of 18 N using machine oil as the lubricant media. The wear rate of the irradiated Ti6Al4V alloy is approximately reduced by 50–70%, compared with that of the non-irradiated alloy. The electrochemical polarization measurement shows that improved corrosion resistance of the irradiated Ti6Al4V alloy is obtained in 1 mol l−1 HCl test solution. We proved that the HIPIB irradiation onto the Ti6Al4V alloy results in combined improvement in wear and corrosion resistance. [Copyright &y& Elsevier]

A series of alloy elements, including the detrimental neutral and beneficial elements for bulk alloying into γ-TiAl base intermetallics, i.e., V, Cr, Y, Er, Nb, and W, has been implanted into a γ-Ti-50Al intermetallic in order to explore the mechanism of high-temperature oxidation resistance for the ionimplanted intermetallic. The oxidation resistance was investigated under cyclic-oxidation conditions at oxidation temperatures from 800 to 1000°C for 200 hr in air. At a lower oxidation temperature of 800°C, the V-ion implantation has a detrimental effect on the oxidation resistance of Ti-50Al, while a neutral and beneficial effect was observed for Er-, Y- and Cr-, Nb-, W-ion implantation, respectively. At 900°C, V-, Er-, Y-, and Cr-ion implantation all showed a neutral effect, whereas Nb- and W-ion implantation apparently improved the oxidation resistance. With increasing oxidation temperature to 1000°C, Y- and Cr-ion implantation kept the neutral effect, and the beneficial effect of Nb-ion implantation disappeared gradually. The oxidation behavior of ion-implanted γ-TiAl base intermetallics is different from that of bulk- alloyed materials due to the two alloying methods, although the effect of the alloy elements on the oxidation resistance has not essentially changed in the γ-TiAl base intermetallics. [ABSTRACT FROM AUTHOR]

Experimentally and theoretically, the basic structures of disordered expanded austenite, γ N , and ordered expanded austenite, γ' N , have been confirmed to consist of Cr-N short-range ordering (SRO) and Fe 4 N-like long-range ordering (LRO) in addition to Cr-N SRO, respectively. So far, the transition from γ N to γ' N during low temperature nitriding has not been elucidated. In present work, four f.c.c. Fe-Cr-Ni alloys with 0, 6, 12 and about 18 wt.% Cr in low-temperature nitrided condition were investigated with transmission electron microscopy (TEM) to explore the evolution from γ N to γ' N. The Fe 4 N-like LRO is present as small ordered domains separated by antiphase boundaries. Ordering of the interstitial nitrogen involves nucleation, growth and, after impingement, coarsening of the ordered domains. The domain size decreases with Cr content and increases with N content in the investigated alloys. A 3-dimensional Cellular Automaton (CA) was developed to simulate nucleation and growth until impingement into full LRO was reached; also the subsequent coarsening stage was simulated. The simulated distributions of ordered domains for the range of Cr contents are consistent with the TEM results. Cr-N SRO plays both a role of promoting nucleation and limiting growth of the ordered domains. Diffraction simulation by Fourier transforming the CA-simulated nitrogen distribution is consistent with the diffraction data and clarifies the different roles of high-density antiphase boundaries and Cr-N SRO on the superlattice reflections. The simulation is further validated by comparison of the predicted distributions of occupied interstices to literature data for Mössbauer spectroscopy and Extended X-ray Absorption Fine Structure. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: High-intensity pulsed ion beam (HIPIB) treatment is a promising technology of surface modification. In this paper, the creep property of 316L stainless steel irradiated by HIPIB at incident energy fluence per shot of 1.1–3.4J/cm2 with 1–10 shots at 700°C have been studied. It is found that the creep property of the treated specimens after 10 shots fluctuates greatly with increasing energy density per shot. HIPIB irradiation at energy density of 1.1J/cm2 and 2.3J/cm2 prolong the creep rupture life and reduce the steady creep rate with respect to the original specimen. In contrast, HIPIB irradiation at 3.4J/cm2 proves to be detrimental, causing a shorter rupture life and a faster steady creep rate. Otherwise, at a fixed irradiation intensity of 2.3J/cm2 per shot, the number of shots has little effect on the creep property of the treated specimens. The specimens irradiated with 1, 5 and 10 shots all have better creep property compared to the control one and the difference between them is not big. The surface morphology and phase structure in the near surface region of the specimens before and after irradiation were analyzed by using scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. It is shown that the HIPIB irradiation can smooth the surface of the specimens, which can restrain the production of the surface crack. And the presence of a preferred orientation implies the treatment creates an intense compression wave and high dislocation density in the surface layer of the irradiated specimens, which hinders the dislocations movement. [Copyright &y& Elsevier]

Abstract: High-intensity pulsed ion beam (HIPIB) treatment is a new technology for surface modification of materials. In this paper, the surface of 316L stainless steel was irradiated by high-intensity pulsed ion beams at ion current density of 100, 200 and 300A/cm2 with 1, 5 and 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. The influence of HIPIB irradiation on the electrochemical corrosion resistance of 316L stainless steel in 0.5mol/L H2SO4 was investigated. The polarization curves show that under the cooperation of the smooth surface and the grain refinement with the selective ablation of impurities, the corrosion resistance of the irradiated samples was improved significantly. [Copyright &y& Elsevier]

Abstract: The Al ion implantation into AZ31 magnesium alloy was carried out in a MEVVA 80–10 ion implantation system at an ion energy of 40–50 keV with an ion implantation dose ranging from 2×1016 to 1×1017 ions/cm2 at an elevated temperature of 300 °C induced by an ion current density of 26 μA/cm2. The concentration–depth profile of implanted Al in AZ31 alloy measured by Rutherford backscattering spectrometry (RBS) is a Gaussian-type-like distribution in a depth up to about 1200 nm with the maximum Al concentration of about 8 at.%. The X-ray diffraction (XRD) analysis revealed the formation of α-Mg(Al) phase, intermetallic β-Mg17Al12, and MgO phase on the Al ion implanted samples. The potentiodynamic anodic polarization curves of the Al ion implanted samples in the 0.01 mol/l NaCl solution with a pH value of 12 showed increases of the corrosion potential and the pitting breakdown potential, and a decrease of the passive current density, respectively. The Al ion implanted samples with 6×1016 ions/cm2 achieved the high pitting breakdown potential to about −480 mV (SCE). In the 0.08 mol/l NaCl solution with pH=12, the Al ion implanted samples with 1×1017 ions/cm2 showed an increased pitting breakdown potential to about −1290 mV (SCE), from around −1540 mV (SCE) of unimplanted samples. It is indicated that different corrosion mechanisms are responsible for improvement in corrosion resistance of the AZ31 magnesium alloy in the NaCl solutions with the varied concentrations. [Copyright &y& Elsevier]

Abstract: Mg–Cu alloy nanoparticles were in situ prepared by a physical vapor condensation method (arc discharge) in a mixture of argon and hydrogen. Four crystalline phases, Mg, Mg2Cu, MgCu2 and MgO, were formed simultaneously during the arc-discharge evaporation. Detailed experiments revealed that nanostructured hydrogen-active phases of Mg2Cu and Mg exhibit enhanced hydrogen absorption kinetics possibly due to the small grain size and surface defects. The maximal hydrogen storage contents of Mg–Cu alloy nanoparticles can reach 2.05±0.10wt% at 623K. [Copyright &y& Elsevier]