Xinxin Ma

Tribological performance of Ti-6Al-4V plasma-based ion implanted with nitrogen

A low-temperature (< 180°C) plasma-based ion implantation (PBII) with nitrogen that did not affect structure and surface morphology of the substrate barely changed the sample dimension. The hardness increasing factor increased with an increase in implantation dose and/or increase in implantation energy, reaching 1.4-1.7 at the lowest plastic penetration of nearly 300 nm. Wear resistance increased greatly after implantation, and increased with decrease in sliding speed. Friction coefficient decreased, and wear resistance increased with an increase in implantation dose and/or energy or when the counterbody AISI 52100 was replaced with Ti-6Al-4V when treated in the same manner as the disc. Both wear of the unimplanted and implanted discs are abrasive-dominated. A tribofilm, mainly made up of wear debris which was transferred from the disc wear-surface formed the wear surface of the counterbody. The observed wear weight increase of the counterbody (Ti-6Al-4V same treated as the disc) with wear cycle could be the result of the transferred wear debris or tribofilm. The formation and transition of tribofilm during the wear process (the morphology, distribution of the wear debris transferred and the adhesion between the tribofilm and the underlying ball wear surface) are important to the tribological properties and wear mechanism of the implanted samples.

Structure and wear behavior of nitrogen‐implanted aluminum alloys*

Aluminum alloys L2, LD2, LF12, LY12, and Al‐4% Cu were implanted at room temperature with nitrogen ions at an energy of 80 keV and dose range of 1×1016–8.3×1017 N+ cm−2. The surface structure and chemical state of the implanted surface layer was investigated by x‐ray photoelectron spectroscopy, transmission electron microscopy and transmission electron diffraction. Hardness measurements were made using a Vickers microhardness tester, and wear tests were carried out using a pin‐on‐disk wear testing machine. The results reveal that implanted nitrogen combines with aluminum to form AlN precipitates at room temperature and nitrogen implantation accelerates the aging process of Al‐4% Cu alloys. The results also reveal that nitrogen implantation increases the hardness and sliding wear resistance of aluminum alloys. The improvements are mainly attributed to the formation of AlN precipitates.

The mechanical properties of an aluminum alloy by plasma-based ion implantation and solution-aging treatment

The age-strengthening 2024 aluminum alloy was modified by a combination of plasma-based ion implantation (PBII) and solution-aging treatments. The depth profiles of the implanted layer were investigated by X-ray photoelectron spectroscopy (XPS). The structure was studied by glancing angle X-ray diffraction (GXRD). The variation of microhardness with the indenting depth was measured by a nanoindenter. The wear test was carried on with a pin-on-disk wear tester. The results revealed that when the aluminum alloys were implanted with nitrogen at the solution temperature, then quenched in the vacuum chamber followed by an artificial aging treatment for an appropriate time, the amount of AlN precipitates by the combined treatment were more than that of the specimen implanted at ambient temperature. Optimum surface mechanical properties were obtained. The surface hardness was increased and the weight loss in a wear test decreased too.

Structure and frictional characteristics of Ti–6Al–4V plasma-based ion implanted with nitrogen then acetylene

Abstract The concentration depth profiles, structure and ball-on-disk frictional characteristics of Ti–6Al–4V plasma-based ion implanted with nitrogen (energy 60 keV) then acetylene (energy 10–30 keV) were investigated. The implanted samples ( R =0.05–2×10 11 Ω cm −1 for the modified layers) included three zones: a top H–DLC zone, a C, N, Ti, O coexisting intermediate zone which had undergone chemical state changes indicating TiN, TiC, and Ti(C,N) second phases were formed, and the bottom zone of the substrate. The samples showed higher hardness especially at low plastic penetrations and higher wear resistance (lower coating brittleness) in the order of 10, 20, 30 and 10, 30, 20 keV implantation, respectively. A tribofilm transferred from disc to ball wear surface was found, lowering friction coefficient and reducing the ball wear, and this result possibly caused the ball weight increase after wear testing. With decreased load and increased speed, the function of the transfer film became more important, and tribological properties were improved (stable friction coefficient 0.15–0.25). When counterbody AISI 52100 was changed to Ti–6Al–4V modified as the disc, initial friction and wear life decreased, and wear was changed from only disc to both disc and ball abrasive dominated. The as-implanted samples demonstrated greatly improved tribological properties compared with unimplanted ones, showing a possible optimal implantation energy.

Characterization of interface of c-BN film deposited on silicon(100) substrate

Abstract The interfacial microstructure of cubic boron nitride (c-BN) film deposited on single silicon substrate using magnetically enhanced active reaction evaporation (ME-ARE) has been investigated through thinning methods, in which X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) absorption spectroscopy were used for compositional and microstructure analysis. c-BN film was etched at size 4×4mm 2 by argon ion in XPS equipment to obtain depth concentration profile of the BN film and B1s XPS spectra at different etching depth. FTIR was alternately used to determine the microstructure of the BN film at different etching depth. The results show that a thin layer of hexagonal boron nitride (h-BN) phase exists at the interface between c-BN layer and substrate. In addition, transmission electron microscopy and selected area electron diffraction further confirm above the conclusion.

Tribological behavior of aluminum alloys surface layer implanted with nitrogen ions by plasma immersion ion implantation

Abstract Some 2014 and 2024 aluminum alloys were implanted with nitrogen ions (N+) by Plasma Immersion Ion Implantation (PIII), and dose range was from 2×1017 to 1×1018 N+ cm−2. The microstructure of surface layer was studied by Transmission Electron Microscopy (TEM). The depth profile of the implanted layer was investigated by Auger Electron Spectrometry (AES). The wear test was carried on a pin-on-disk wear tester. The micro-morphology of wear was observed by Scanning Electron Microscopy (SEM). The results reveal that: after implanted with nitrogen ions, the friction coefficient of surface layer decreased, and the relative wear resistance increased with the increase of the nitrogen dose. The tribological mechanism was mainly adhesive, and the adhesive wear tended to become weaker gradually with the increase of nitrogen dose. The upper two effects were mainly attributed to the formation of hard AlN precipitation and supersaturated solid solution of nitrogen in the surface layer.

Structure of titanium films implanted with carbon by plasma-based ion implantation

Abstract By combining plasma-based ion implantation with unbalanced magnetron sputtering deposition, ion implantation mixed films were prepared on steel 45 substrate. X-ray photoelectron spectroscopy analysis shows that the concentrations of carbon and titanium have a periodical distribution in the prepared films. It comes from the periodical deposition and ion implantation process. The binding energy of C1s in the film varies with implantation depth, corresponding to the variation of the carbon distribution. It is found by glancing angle X-ray diffraction that TiC phase exists in the mixed films and the elemental titanium is not in a state of crystalline structure.

Tribological behaviour of duplex treated Ti–6Al–4V: combining nitrogen PSII with a DLC coating

Abstract The chemical structure and tribological behaviour of Ti–6Al–4V plasma source ion implanted with nitrogen then DLC-coated in an acetylene plus hydrogen-glow discharge (bias voltage −10 to −30 kV) were investigated. The as-modified samples have a TiN/H:DLC multilayer architecture (coating resistivity 1.6×10 9 to 2.4×10 11 Ω/cm) and exhibit higher hardness, especially at low loads or plastic penetrations in the order of deposition bias voltage −10, −20 and −30 kV. At a lower contact load (1 N) and higher sliding speed (0.05 m/s), frictional properties in most cases improved, as did wear properties. At a higher contact load (5 N) and lower sliding speed (0.04 m/s), friction showed almost no improvement, and wear properties deteriorated. When the material of the counterbody was then changed from AISI 52100 to Ti–6Al–4V modified as the disc (contact load 5 N unchanged, sliding speed decreased), the friction coefficient decreased (but showed no improvement compared with the unmodified sample), while wear properties deteriorated further, and wear was changed from just the disc to both disc and ball, abrasive and adhesive dominated. Transfer films, mainly made up of wear debris transferred from the disc wear surfaces, were formed on the wear scars of the counterbodies. The deterioration of wear properties of the modified samples at the higher contact load is considered to be caused by the “thin ice” effect.

Coating and ion implantation to the inner surface of a pipe by metal plasma-based ion implantation and deposition

This article describes the characteristics of the coating of the inner surface of a pipe using plasma-based ion implantation and deposition method with a d.c. titanium-cathodic-arc in nitrogen gas. It was confirmed that the coating of the inner surface of the pipe with titanium nitride film was possible by using this method. The film structure and preferential orientation can be controlled by the applied voltage to the pipe. The film on the inner surface of a pipe in its entrance region showed an oriented columnar grain structure oblique to the substrate. The surface morphology changed with the waveform of the applied voltage. These characteristics were closely related to the dynamic behavior of the ions.

Preparation of Ti/N and Ag/TiNx Multilayers by Plasma Based Ion Implantation With Multi-Targets Unbalanced Magnetron Sputtering

Ti/N and Ag/TiNx multilayers were prepared by plasma based ion implantation (PBII) with multi-targets unbalanced magnetron sputtering and analyzed by Auger electron microscopy (AES) and X-ray photoelectron spectroscopy (XPS). Nitrogen plasma gas and Ti and Ag multi-targets were used in this study. It was found that both gases and metal elements could be implanted into the samples. Ti/N and Ag/TiNx multilayers were successfully fabricated by multi-cycle PBII with nitrogen plasma gas and Ti and Ag unbalanced magnetron sputtering. The possibility of design and fabrication of multilayers by this technique is also discussed. This technique for the deposition of films may find more applications.