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Abstract: The wear resistance and wear mechanism of AZ31 magnesium alloy irradiated by high-intensity pulsed ion beam (HIPIB) at an ion current density of 100A/cm2 with shot number from one to ten are investigated by dry sliding wear tests. The cross-sectional microstructure and surface microhardness of the irradiated AZ31 magnesium alloys are examined by optical microscopy (OM) and Vickers tester, respectively. It is found that surface hardness increased with increasing shot number, from an original value of 570MPa to a maximal value of 820MPa with ten shots, and the wear rate of the samples irradiated with five and ten shots was about one order of magnitude less than that of the original sample. The transition from severe metallic wear to mild oxidative wear induced by HIPIB irradiation was identified through a combined analysis in surface morphology and chemical composition of wear tracks, mechanically mixed materials, wear debris and wear scars of counterface steel ball by using scanning electron microscopy (SEM) and electron probe microanalysis (EPMA), which is mainly attributed to the significant increase in microhardness resulting from grain refinement on the irradiated surface. [Copyright &y& Elsevier]

Abstract A series of copper thin films on Si(100) substrate were deposited using the modulated pulsed power magnetron sputtering under a sputtering pressure from 0.11 to 0.70 Pa. The scratch behavior of Cu/Si(100) thin films was characterized by the critical loads (Lc1–4) with the aid of finite element method (FEM) simulation. Increasing the sputtering pressure, surface morphology became rougher and the cross-sectional pattern transformed from compact fine granular to coarse and crack visible columnar structure. The Cu thin films scratched were continuous and comparative intact at 0.11 Pa which occurred to be with the highest critical loads, then gradually went to vast delamination initiated at 0.30 Pa with the Lc decreasing accordingly. The maximum principal stress (σ 1) calculated by FEM was employed to evaluate the transition of critical loads Lc1–Lc4 using the typical stress concentration zones A, B and C which were the zones under, around and at the sides of the scratch tip, respectively. For the Cu/Si(100) thin films with strong adhesion, the Lc1 and Lc2 were evaluated through the migration of σ 1 peak from the zone B to C, while the Lc3 and Lc4 were associated with stress accumulation at the zone C and A. The scratch behavior of Cu/Si(100) thin films was quantitatively expressed with the aid of FEM simulation. Highlights • Scratch behavior of Cu/Si(100) thin films deposited by MPPMS was characterized. • Typical plastic deformation features appeared on the scratched Cu/Si(100) films. • High critical loads of Lc1–4 resulted by fine granular microstructure of Cu films. • Lc1–4 dependent on migration and accumulation of the maximum principal stress by FEM • Scratch behavior of Cu/Si(100) films was quantitatively related to FEM modelling. [ABSTRACT FROM AUTHOR]

CrN/TiN multilayer coatings were deposited by pulsed dc magnetron sputtering (PDCMS) in a closed field unbalanced magnetron sputtering system. The Ti target power was maintained at 2000 W while the Cr target power was varied from 70 to 1000 W. As the Cr target power was increased, CrN/TiN multilayer coatings with the Cr/(Cr + Ti) ratio of 0.037–0.573 had a single phase face-centered cubic structure with a texture evolution from (111) to (220). The residual stress of the coatings increased from − 1.03 GPa to − 5.65 GPa. The hardness and the H/E* and H 3 /E* 2 ratios of the coatings exhibited an initial increase with the increasing Cr target power, then followed by a decrease. The coating with a Cr/(Cr + Ti) ratio of 0.30 reached the highest hardness and the H/E* and H 3 /E* 2 ratios of 31 GPa, 0.0832 and 0.214, respectively. The coating also showed a dominant oxidative wear with the lowest friction coefficient and specific wear rate of 0.41 and 2.3 × 10 − 6 mm 3 N − 1 m − 1 , respectively. The increase in the H/E* and H 3 /E* 2 ratios led to the increase in the toughness and cohesion/adhesion strength of the coatings with the increased HF levels and critical loads ( L C1 , L C2 and L C3 ). However, the coatings with similar H/E* and H 3 /E* 2 ratios exhibited different tribological properties due to the different critical loads L C3 resulted from the increased compressive residual stress. The improvements in toughness and cohesion/adhesion strength promoted the reduction in the crack initiation and propagation, and oxidative wear during dry sliding tests. [ABSTRACT FROM AUTHOR]

The plasma polymerization of ethanol monomer was carried out under the capacitively coupled radio frequency plasma (CCP) of a radio frequency (RF) power of 100 W at different power to flow rate (P/F) ratios of 0.7, 1.0 and 2.7 W/sccm. The influence of the P/F ratios on deposition rate, chemical composition, surface morphology, and wettability were studied for the plasma polymer films of ethanol monomer on the pristine low density polyethylene (LDPE) surfaces and the surfaces under the oxygen CCP pretreatment of a RF power of 200 W for an exposure time of 1 and 5 min. The deposition rate of the plasma polymer films gradually increased with the P/F ratios. The retention of the hydroxyl groups decreased and the contents of the ketone, carboxylic acid, ester, ether, and epoxide groups increased in the plasma polymer films with the increased P/F ratios. The conformal deposition of the plasma polymer films to the LDPE surfaces was found on the pristine surfaces with the sub-micrometer asperities and the surfaces under oxygen CCP pretreatment with the nanotextures. The dynamic contact angle of the plasma polymer films increased with the P/F ratios on the LDPE surfaces with the sub-micrometer asperities. The plasma polymer films showed the decrease of the dynamic contact angle with the P/F ratios on the surfaces with the nanonodules and the nanopillar array. The significant improvement of the adhesion was achieved for LDPE samples with the nanonodules and the nanopillar array under the surface modification of the oxygen CCP pretreatment followed by the deposition of the plasma polymer films of ethanol monomer due to the cooperation adhesion mechanisms of the mechanical interlocking and the chemical bonding. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline Cr–C–N coatings were deposited by pulsed closed field unbalanced magnetron sputtering. The microstructure, chemical composition and elemental chemical state of the coatings were investigated using field-emission scanning electron microscopy, glancing incident angle x-ray diffraction and x-ray photoelectron spectroscopy. Mechanical and tribological properties of the coatings were measured by nanoindentation and ball-on-disk wear tests. The Cr–C–N coatings consist of nanocrystalline Cr7C3, CrN embedded in an amorphous carbon and CN matrix. The coatings with a N content of 25.5 at.% possessed a highest hardness of 25.4 GPa and a highest H/E ratio of 0.096. Dependent on the C content, the steady state dry coefficient of friction values for Cr–C–N coatings sliding against a WC-Co ball were found in the range of 0.38–0.56. The wear rates of the coatings are in the low range of 1.28–3.44×10−6 mm3 N−1 m−1. [Copyright &y& Elsevier]