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Clean-integrity processing of nuclear-grade AISI 316L austenitic stainless steel components finished by the wire brush and sequent flap discs is performed for high-performance manufacturing of the nuclear power plant equipment. Two steel wire brushes of AISI 304 austenitic stainless steel and 65Mn carbon spring steel are used for the grinding under a spindle speed of 550–2000 rpm. Sequent polishing is carried out by the flap discs using silicon carbide cloth under 2000 rpm. An equivalent pitting corrosion resistance to that of the original stainless steel in 3.5% NaCl solution is obtained for finished samples by the combined processes. The contaminants composition of ground stainless steel samples is determined by the redness degree of chromaticity inspection. The contaminants microstructure and finishing-induced microstructure are dependent on the impedance phase angle change in eddy current impedance diagrams. The surface clean-integrity of nuclear-grade stainless steel is characterized by the series of nondestructive evaluation methods. [ABSTRACT FROM AUTHOR]

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: 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]

Abstract: The Al ion implantation into AZ31 magnesium alloy is carried out in a MEVVA 80-10 ion implantation system with an ion implantation dose ranging from 2×1016 ions/cm2 to 1×1017 ions/cm2 at an ion energy of 40–50 keV. The concentration–depth profile of implanted Al in AZ31 magnesium alloy was a Gaussian-type distribution in the depth up to about 840 nm with the maximum Al concentration up to about 10 at.% measured by using Rutherford backscattering spectrometry (RBS). The microstructure, which is composed of α-Mg phase, intermetallic β-Mg17Al12 and MgO phases is observed on the ion implanted samples by X-ray diffraction (XRD). Potentiodynamic anodic polarization curves in 0.01 M NaCl solution with pH=12 showed that the increase of corrosion potential and pitting breakdown potential and the decrease of the passive current density are obtained for the Al ion implanted samples. The Al ion implanted AZ31 magnesium alloy with the ion implantation dose of 2×1016 ions/cm2 achieved the high pitting breakdown potential to about −1000 mV(SCE). The wear rate of the Al ion implanted AZ31 magnesium alloy is approximately reduced by 30–40%, compared with that of the unimplanted sample. [Copyright &y& Elsevier]

Abstract: Plasma-based low-energy 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 steel and alloys. In this work, the effects of nitrogen alloying on the wear and corrosion resistance of the plasma source ion nitrided 1Cr18Ni9Ti austenitic stainless steel have been investigated in order to produce a combined improvement in wear and corrosion resistance. A high-nitrogen face-centered-cubic (f.c.c.) phase (γN) with the different nitrogen contents formed on the nitrided stainless steel was characterized using Auger electron spectroscopy, electron probe microanalysis, glancing-angle X-ray diffraction and transmission electron microscopy. The wear tests were performed on a pin-on-disc tribometer in which the γN-phase samples were rubbed against a hardened Cr12MoV high-alloy steel disc (HRC 62–63) under a normal load from 2.2 to 39 N using Cr2O3 powders in machine oil as the abrasive media. The corrosion resistance was analyzed in 1% NaCl and 0.5 mol l−1 H2SO4 solutions by the electrochemical polarization technology. The γN-phase samples have a high microhardness of about HK0.1N 22 GPa and a high load-bearing capability, leading to significant improvement in wear resistance, especially under the high normal loads. The high nitrogen content in the γN phase resulted in higher wear resistance through the formation of a thicker hardened layer. The γN-phase samples have a high pitting corrosion resistance and a similar general corrosion resistance compared with those of the original stainless steel. The nitrogen content in the γN phase mainly affected the pitting corrosion resistance and slightly affected the general corrosion resistance. [Copyright &y& Elsevier]

Deep oscillation magnetron sputtering (DOMS) is a novel high power impulse magnetron sputtering technique, which offers large voltage oscillation packets to generate a stable high-power discharge plasma with high ionization under virtually arc-free conditions. CrN/TiN superlattice coatings with various modulated periods (Λ) were deposited by the combined DOMS and pulsed dc magnetron sputtering. CrN/TiN superlattice coatings with the Cr/(Cr + Ti) ratio ranging from 0.177 to 0.496 exhibited a single phase face-centered cubic structure with a strong (111) texture. As the Λ was increased from 5.7 to 10.2 nm, the residual stress was increased from − 2.1 to − 5.6 GPa. The increase in Λ led to an initial increase, followed by a decrease in hardness, and the H/E* and H 3 /E* 2 ratios. The coating at Λ = 6.3 nm showed the highest adhesion with the highest HF level in Rockwell C tests and critical loads in scratch tests due to the highest hardness of 36 GPa, H/E* ratio of 0.093 and H 3 /E* 2 ratio of 0.316. The predominant adhesive failure mode in scratch tests was buckling failure independent of the changes of Λ and substrate hardness. However, the increase in substrate hardness resulted in an increase in critical loads ( L C1 , L C2 , L C3 and L C4 ), especially for a significant increase in L C3 , due to the increased cooperative deformation of a coating/substrate system by increasing toughness of coatings, cohesion/adhesion and substrate hardness. The increased adhesion was responsible for the increased pitting and stress corrosion cracking resistance in 3.5 wt.% NaCl aqueous solution due to the optimized Cr/(Cr + Ti) ratio and Λ. [ABSTRACT FROM AUTHOR]

Deep oscillation magnetron sputtering (DOMS) is a novel high power impulse magnetron sputtering technique, which offers large voltage oscillation packets to generate a stable high-power discharge plasma with high ionization under virtually arc-free conditions. CrN/TiN superlattice coatings were deposited using a combined DOMS and pulsed dc magnetron sputtering (PDCMS) in a closed field unbalanced magnetron sputtering configuration. The Cr target was powered at 400 W by DOMS and Ti target was powered at 2000 W by PDCMS. The negative substrate bias ( V s ) ranged from 0 V to −100 V. As the V s was increased, CrN/TiN superlattice coatings showed a single phase face-centered cubic structure with a strong (1 1 1) texture. Correspondingly, the coatings exhibited the dense microstructure with well-defined interfaces between CrN and TiN layers. The increase in V s led to a decrease in grain size and an increase in the compressive residual stress. The hardness and Young's modulus of the coatings increased with increasing V s . The H / E * and H 3 / E * 2 ratios and critical loads L C in scratch test showed an initial increase, followed by a decrease. The wear mechanism changed from severe adhesion wear to abrasion wear. The coating deposited at V s = −60 V exhibited mild abrasion wear with the lowest friction coefficient of 0.27 and the lowest specific wear rate of 0.5 × 10 −6 mm 3 N −1 m −1 due to high hardness, H / E * and H 3 / E * 2 ratios, L C1 and L C3 of 36 GPa, 0.094, 0.316, 15.3 N and 24 N, respectively. The coatings also exhibited increasing pitting corrosion resistance with lower current density and higher corrosion potential in 3.5 wt% NaCl aqueous solution. Combined DOMS + PDCMS techniques can provide the engineering surfaces for the industrial applications with the combined improvement in wear and corrosion resistance. [ABSTRACT FROM AUTHOR]

Abstract: The wear and corrosion resistance of AZ31 magnesium alloy irradiated by high-intensity pulsed ion beam (HIPIB) at an ion current density of 100–300A/cm2 with shot number of 1–10 are investigated by sliding wear test and potentiodynamic polarization measurement. The surface and cross-sectional morphologies, phase structure and surface microhardness of the irradiated AZ31 magnesium alloy samples are characterized by scanning electron microscopy (SEM), optical microscopy, X-ray diffraction (XRD) and Vickers tester, respectively. The HIPIB irradiation produces the hardened surface layers and improves abrasive wear resistance of all the samples. The wear volume of the irradiated samples at 200A/cm2 and 300A/cm2 with 10 shots as well as 100A/cm2 with 5 shots is about four times less than that of the original sample. The apparent increase in corrosion resistance is achieved for all the irradiated samples in 0.01mol/l NaCl solution with a pH value of 12. The corrosion potential and pitting breakdown potential for the samples irradiated at 100A/cm2 with 5 shots are 560 and 630mV higher than those of the original sample, −1560mV and −1300mV (SCE), respectively. It is found that the combined improvement in wear and corrosion resistance of AZ31 magnesium alloy is achieved by HIPIB irradiation, which is ascribed to the microstructural refinement and the chemical homogeneity of the irradiated magnesium alloy. [Copyright &y& Elsevier]