Plasma Surface Alloying Technique Research Articles

A study on tribological behavior of double-glow plasma surface alloying W-Mo coating on gear steel

In the present study, a dense W-Mo coating was formed onto the gear steel by using double-glow plasma surface alloying technique. The nanoindentation test was used to measure the hardness and elasticity modulus of the coating. The scratch test was applied to evaluate the critical load for coating delamination, which measured the adhesion strength of the coating. The tribological behavior of the W-Mo coating was estimated using a pin-on-disc tribometer by rubbing against the Si3N4 ceramic ball. Results showed that the W-Mo coating was well diffusely bonded to the substrate. In terms of the H/E and H3/E2 ratios, the coated sample was nearly two times greater than that of the uncoated sample. The specific wear rates of the W-Mo coating at room and high temperature were 8.1×10−5 mm3N−1m−1 and 11.2×10−5 mm3N−1m−1 respectively, about only 19% of that of the uncoated sample. The excellent wear resistance of the W-Mo coating may be due to its high resistance to plastic deformation and good load bearing capacity.

A comparative study of the corrosion performance of titanium (Ti), titanium nitride (TiN), titanium dioxide (TiO2) and nitrogen-doped titanium oxides (N–TiO2), as coatings for biomedical applications

The performance of four titanium coatings, namely, Ti, TiN, TiO2, and N–TiO2 was assessed in terms of their surface properties and electrochemical corrosion in simulated body fluid in relation to their medical applications. Ti, TiN, TiO2, and N–TiO2 coatings were deposited onto stainless steel substrates by a plasma surface alloying technique. Morphology, composition, and structure were investigated by SEM, GDOES, and XRD. Corrosion resistance results indicated that Ti, TiN, TiO2, and N–TiO2 coatings could achieve higher corrosion polarization resistance and a more stable corrosion potential in the SBF environment than the uncoated stainless steel substrate SS316L. In comparison with the Ti, TiN, and TiO2 coatings, the N–TiO2 coating exhibited superior corrosion resistance. This resistance may be attributed to the multilayered structure of the coating (an outer oxidative layer and an inner diffusion zone of Ti and N), which can hinder the diffusion of reactive ions.

Tribological Behavior of Plasma Mo-Alloyed Layer on TC11 Alloy under Different Loads

Abstract The tribological behavior and wear mechanism of a Mo-alloyed layer prepared by a double-glow plasma surface alloying technique were investigated under different loads. The microstructure, the composition distribution and the phase structure of the Mo-alloyed layer were characterized by SEM, EDS and XRD, respectively. The results show that the uniform and compact Mo-alloyed layer with 20 μm thickness is composed of phases Mo, Al 3 Ti and Al 8 (Ti 3- x Mo x ). The sliding wear experiments were performed under different loads (1.3, 5.3 and 9.3 N) in order to examine the tribological properties of the Mo-alloyed layer. The average friction coefficients and the wear rates of Mo-alloyed layer both show an upward tendency with the increased of loads. Mild abrasion wear and oxidative wear could be detected under 1.3 N load based on the analysis results of 3D surface morphologies, SEM and EDS. The wear mechanism under 5.3 N load is dominated by oxidative wear and abrasion wear. Oxidative wear, abrasion wear and adhesive wear are the main wear mechanism under 9.3 N.

Influence of zirconium alloying layer on properties of TC11 alloy

Zirconium (Zr) alloying layer was formed in the TC11 surface by using the double glow plasma surface alloying technique. The microstructure, surface hardness and oxidation resistance of the alloying layer were investigated by X-ray diffraction, scanning electron microscope and energy dispersive X-ray spectrometry, respectively. The results showed that the alloying layer consisted of a compact and homogeneous Ti–Zr mutual diffusion layer, and the surface alloying elements all displayed gradient distributions. The zirconium alloying layer enhanced the surface hardness by solution strengthening. The improvement of TC11 oxidation resistance was due to the formation of compact and uniform oxide scales, which was consisted of ZrO2 as the major phase and TiO2 as the minor phase.

Nano-mechanical characterization of plasma surface tungstenized layer by depth-sensing nano-indentation measurement

Plasma surface tungstenizing was performed on Ti–Al–Nb substrate using the double-glow plasma surface alloying technique. The microstructure and composition of the tungstenized layer were determined by scanning electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy. The mechanical properties of the substrate and the tungstenized layer were characterized by the dynamic micro-hardness and the elastic modulus. The results showed that the tungstenized layer was comprised of three distinct sub-layers namely sediment layer, transition layer and diffusion layer, with a total layer thickness of over 25μm. The concentration of the tungsten decreased gradually as the layer depth increased and the continuous change in the tungsten content affects the mechanical properties of the alloyed layer. The dynamic micro-hardness and elastic modulus of the tungstenized layer and substrate were investigated by the depth-sensing nano-indentation measurement under different conditions. According to the findings, the values of dynamic micro-hardness exhibited no significant dependence on the indentation load. However, the elastic modulus of the tungstenized layer tended to decrease as the indentation load was increased. Furthermore, the dynamic micro-hardness and elastic modulus curves of the tungstenized layer revealed a pattern similar to the concentration distribution of the tungsten. Both surface micro-hardness and elastic modulus of plasma alloyed surface gradually decreased with the increase of indentation depth, most probably because of the three different regions in the alloyed layer. As for the mechanical properties, the tungstenized layer exhibited significantly higher dynamic micro-hardness and elastic modulus than the substrate. As the cyclic loading–unloading curves of the substrate and the tungstenized layer showed, the elastic recovery and uniform plastic deformation decrease and the fatigue damage of the tungstenized layer is lower than that of the substrate.

Low temperature plasma surface alloying and characterisation of a superduplex stainless steel

AbstractBecause of their superior mechanical properties and high corrosion resistance in aqueous environments, duplex stainless steels are the material of choice for equipment used in the off-shore gas and oil industry. However, wear in chloride containing water (i.e. corrosion wear) is considered as a major concern. During the past decade, a new low temperature plasma surface alloying technique has been developed to achieve combined improvements in hardness, wear resistance and fatigue properties of austenitic stainless steels, without impairing their corrosion behaviour due to the formation of S-phase. However, few researchers have applied this technique to duplex stainless steel (DSS) and no work has been reported for super DSS (SDSS). In this paper, SDSS 2507 has been DC plasma nitrided under a range of treatment conditions. Energy dispersive X-ray spectroscopy (EDX), Glow discharge Spectrometry (GDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterise the microst...

Assessments on corrosion, tribological and impact fatigue performance of Ti- and TiN-coated stainless steels by plasma surface alloying technique

In this work, Ti and TiN coatings were deposited on AISI316L stainless steel (SS) substrates by plasma surface alloying technique. The morphology, composition and structure were investigated by SEM, GDOES and XRD. The corrosion properties of Ti and TiN coatings were investigated in a simulated body fluid (SBF) environment. Friction and wear behaviors of SS substrates and Ti and TiN coatings were measured using a ball-on-disk type tribometer under sliding against Si3N4 counterparts under boundary lubricated conditions with either normal saline or SBF. The ball-on-plate impact tests were conducted on the coatings under a constant force of 800N for 10,000 impacting cycles. The results indicate that the Ti and TiN coatings could achieve a higher corrosion polarization resistance and a more stable corrosion potential in the SBF environment than the uncoated stainless steel substrate SS316L. The Ti and TiN coatings also exhibited an excellent wear resistance and chemical stability during the sliding tests against Si3N4 ball in normal saline and SBF environment. The tested samples showed different wear mechanisms in the sliding tests. Compared to the Ti coatings, the TiN coatings had a better compatibility with the Si3N4 ball. However, the impact tests showed that the fatigue cracks and the coatings' chipping occurred on the TiN coatings but not on the Ti coatings.

Structural, tribological and antibacterial activities of Ti–Cu–N hard coatings prepared by plasma surface alloying technique

In this work, Ti–Cu–N hard coatings were deposited on AISI316L stainless steel (SS) substrates by plasma surface alloying technique with a Ti–Cu alloy target. The morphology, composition and structure were investigated by SEM, GDOES and XRD. Microhardness and coating/substrate adhesion were analyzed by microhardness tester and scratch test. Tribological performance of the Ti–Cu–N coatings and SS substrate was investigated by using ball-on-disk tribometer. The viability of bacteria attached to the antibacterial surface was tested using the spread plate method. The results indicated that the concentration of Ti and Cu gradually decreased from the surface coatings to substrate, and the maximum copper concentration in the alloyed surface was about 20wt.%. X-ray diffraction analysis showed that the coatings were composed of TiN and copper crystalline phases. Scratch test showed that the Ti–Cu–N coatings possessed good adhesion with the substrate. The microhardness of the Ti–Cu–N coatings was about 1030 HV0.025, which was about 4.5 times as much as that of the SS substrate. Wear resistance of the Ti–Cu–N coatings was improved obviously during the sliding tests against GCr15, and showed micro-abrasion wearing. The Ti–Cu–N coatings exhibited excellent antibacterial ability, and an effective reduction of 99.9% of Escherichia coli (E. coli) within 12h was achieved by contact with the alloyed surface, which may be attributed to the release of copper ions when the Ti–Cu–N coatings in contact with bacterial solution.

THERMALLY OXIDIZED C, N CO-DOPED ANATASE-TiO2 COATINGS ON STAINLESS STEEL FOR TRIBOLOGICAL PROPERTIES

Ti ( C , N ) coatings were prepared on stainless steel (SS) substrates by plasma surface alloying technique. Carbon–nitrogen co-doped titanium dioxide ( C - N - TiO 2) coatings were fabricated by oxidative of the Ti ( C , N ) coatings in air. The prepared C - N - TiO 2 coatings were characterized by SEM, XPS and XRD. Results reveal that the SS substrates were entirely shielded by the C - N - TiO 2 coatings. The C - N - TiO 2 coatings are anatase in structure as characterized by X-ray diffraction. The tribological behavior of the coatings was tested with ball-on-disc sliding wear and compared with substrate. Such a C - N - TiO 2 coatings showed good adhesion with the substrate and tribological properties of the SS in terms of much reduced friction coefficient and increased wear resistance.

Microstructure, antibacterial properties and wear resistance of plasma Cu–Ni surface modified titanium

A Cu–Ni alloyed layer on titanium was obtained by using a plasma surface alloying technique to improve antibacterial activity and wear resistance. The microstructure and phase constituents of Cu–Ni alloyed layer were characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The antibacterial properties and wear resistance of treated titanium were investigated. The results show that the Cu–Ni alloyed titanium exhibits high antimicrobial activity to Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) due to the formation of Cu-containing phase. Moreover, the Cu–Ni alloyed layer can greatly improve the hardness and wear resistance of pure titanium. It is expected that the Cu–Ni alloyed titanium combining excellent bactericidal ability with wear resistance might provide a durable antibacterial function for biomedical application.

Zr-N surface alloying layers fabricated in pure titanium substrates by plasma surface alloying

The Zr-N alloying layers were prepared on the surface of pure titanium substrates by plasma surface alloying technique to improve the surface properties. The microstructure, chemical composition, and hardness of Zr-N surface alloying layers were analyzed to understand the mechanisms of surface alloying and hardness improvement. The tribological performance of Zr-N surface alloying layers was studied by ball-on-disc wear machine. The results show that Zr-N alloying layers formed are homogeneous and compact. The Zr-N surface alloying layer consists of an outer nitride layer and an inner diffusion zone of zirconium and nitrogen. The surface treatment enhances the hardness of the surface layers of pure titanium substrates greatly and a surfaces hardness of HK1870 is obtained. Though Zr-N surface alloying layer does not show friction-reducing effect, it improves the wear resistance of pure titanium obviously.

Characterization of Mo surface modified Ti by indentation techniques

Using the plasma surface alloying technique, the Mo modified layers on Ti substrates were obtained. Being duplex, the Mo modified layer contains a Mo deposition layer and a Mo diffusion layer. Microindentation tests were performed on the surface of the Mo modified layer by two loading types, i.e. linear loading type and continuous multi-cycle loading type which can link the nano and micro range indentation values. In the microindentation process, acoustic emission testing was adopted in order to investigate cracking of the Mo modified layer. Nanoindentation tests were performed not only on the cross section of the Mo modified Ti, but on the surface of the untreated Ti plate (before alloying treatment). The experimental results indicate that the whole Mo modified layer possesses higher hardness, elastic modulus and remains relatively fine plasticity. Better than the hard film/soft substrate system, the graded Mo diffusion layer could coordinate the deformation between the Mo deposition layer and the Ti substrate.

Photocatalytic activities of N doped TiO2 coatings on 316L stainless steel by plasma surface alloying technique

Nitrogen doped titanium dioxide (N-TiO2) coatings were fabricated by oxidation of the TiNx coatings in air. TiNx coatings were prepared on stainless steel (SS) substrates by plasma surface alloying technique. The reference TiO2 sample was also deposited by oxidation of the Ti coatings in air. The as-prepared coatings were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and ultra violet-visible absorption spectroscopy (UV-Vis). The formation of anatase type TiO2 is confirmed by XRD. SEM measurement indicates a rough surface morphology with sharp, protruding modules after annealing treatment. The band gap of the N-doped sample is reduced from 3.25 eV to 3.08 eV compared with the undoped one. All the N-doped samples show red shift in photoresponse towards visible region and improved photocurrent density under visible irradiance is observed for the N-doped samples. The photocatalytic activity was evaluated via the photocatalytic oxidation of methylene blue (MB) in aqueous under visible light irradiation. The results reveal that the N-doped samples extend the light absorption spectrum toward the visible region. The degradation rate of N-TiO2 is 20% in visible irradiation for 150 min.

Preparation of TiAl–Cr surface alloy by plasma-surface alloying technique

A plasma-surface technique was used to form a TiAl–Cr alloy on the surface of a TiAl-based alloy. The feasibility of the alloying process was evaluated by a first principle calculation method. The preparation process was optimized by investigating the effects of processing temperature and discharge pressure on the formation of surface alloy. The calculation using the first-principle method showed that the addition of Cr into the TiAl lattice would increase the stability of the system, and improve mechanical properties of the alloy. The processing temperature was selected at 1100 °C, slightly below the eutectic temperature of the Ti–Al system, ensuring diffusion efficiency and also avoiding the degradation of substrate microstructure. The optimum discharge pressure was 25 Pa within the range of 12–55 Pa. Sputtering and diffusion were well coordinated at this pressure and the obtained alloyed layer had the largest thickness.

Tribology behavior of double-glow discharge Mo layers on titanium alloy in aviation kerosene environment

In order to improve the tribology behavior in aviation kerosene, molybdenum (Mo) modified layers were fabricated on Ti6Al4V base alloy using a double-glow plasma surface alloying technique. The morphology, microstructure, microhardness and element depth distribution of the Mo modified layers were studied. The tribology properties of Ti6Al4V base alloy, Mo modified layers and 5CrMnMo tool steel sliding with GCr15 steel or QSn4-3 copper alloy counterparts in aviation kerosene were comparatively researched. The effect of roughness on the sliding wear behavior was discussed. The results indicate that the Mo modified layers with polishing treatments not only reduce the friction coefficient of Ti6Al4V base, but also enhance the wear resistance of the counterparts. The Mo modified layers have better tribology behavior than 5CrMnMo steel. It is also found that the wear volume loss of the counterparts is proportional to the value of roughness of Mo modified layers, which is related directly to the ploughing wear between micro convex bodies of the layers and counterparts.

Improved oxidation resistance of the Zr-alloyed layer formed on 420 stainless steel by plasma surface alloying

A Zr-alloyed layer is prepared on the 420 stainless steel by plasma surface alloying technique in order to improve its poor elevated temperature property. The oxidation behavior of the Zr-alloyed stainless steel is studied in the paper. It is found that the Zr-alloyed layer with approximately 5μm in thickness is bonded strongly to the steel substrate and consists of ZrC, Cr23C6 and metallic Zr. The result of a cycling oxidation at 1000°C indicates that the mass gain of Zr-alloyed specimens is only 0.9mg/cm2 after exposure for 100h in air, exhibiting an excellent oxidation resistance. A thin oxide scale formed on the alloyed stainless steel is compact and strongly adheres to the oxidized substrate. The improvement of the oxidation resistance for the Zr-alloyed 420 steel is attributed to the formation of a stable outer ZrO2-rich layer and the Cr2O3-rich layer between the inner Fe3O4+Cr2O3 oxide and the substrate.

Bacteria adherence properties of nitrogen-doped TiO2 coatings by plasma surface alloying technique

In order to obtain a high-performance surface on 316L stainless steel (S. S) that can meet the requirements in medical material field environment, nitrogen-doped titanium dioxide (TiO2−x N x ) was synthesized by oxidative annealing the resulted TiN x coatings in air. Titanium nitride coatings on 316L S. S were obtained by plasma surface alloying technique. The as-prepared coatings were characterized by X-ray diffraction, glow discharge optical emission spectrometer (GDOES), scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The bacteria adherence property of the TiO2−x N x coatings on S. S on the oral bacteria Streptococcus Mutans was investigated and compared with that of S. S by fluorescence microscopy. The mechanism of the bacteria adherence was discussed. The results show that the TiO2−x N x coatings are composed of anatase crystalline structure. SEM measurement indicates a rough surface morphology with three-dimensional homogenous protuberances after annealing treatment. Because of the photocatalysis and positive adhesion free energy, the TiO2−x N x coatings inhibit the bacteria adherence.

Tribological and impact fatigue behaviors of pure titanium treated by plasma Ni alloying

Ni modified layer is prepared on the surface of pure titanium by plasma surface alloying technique. Surface appearance, micro-structure morphology, composition distribution, phase structure and microhardness of Ni modified layer are analyzed. Tribological performance and fatigue behaviors of Ni modified layer of pure titanium are observed using Pin-on-disc tribometer and repeated impact test. The results indicate that the surface mean Ni concentration of Ni modified layer is nearly 18% which is composed of TiNi, Ti2Ni and Ti phase. The maximum surface microhardness of Ni modified layer is approximately 580 HV which is almost two-fold of the hardness of the substrate. The wear resistance of Ni modified layer is improved obviously. The wear mechanism of Ni modified layer shows slight abrasion wearing, while pure titanium is abrasion and adhesion wearing. Ni modified layer presents better impact fatigue strength.

Enhanced plasma boriding with molybdenum using double glow plasma surface alloying technique

Double glow plasma surface alloying (DG-PSA) has been studied and applied in surface alloying field for more than 20years, in which the alloying elements were always adopted with metal elements, such as Mo, W, Ni and Nb. Recently, this technology has been used for boriding applications through supplying boron with solid boride medium for its no toxic waste. In present paper, boriding and molybdenum alloying were carried out simultaneously by DG-PSA method, which formed a modified layer consisting of an inner Mo–B diffusion layer and an outer Mo–Fe–B composites deposition coating. The results revealed that molybdenizing and boriding hybrid treatment with a special structural source cathode made a remarked increase in deposition rate and the as-formed layers showed a very good adherence due to its metallurgy bonding.

Friction and wear behaviors of Mo–N modified Ti6Al4V alloy in Hanks' solution

A Mo–N surface modified layer on Ti6Al4V alloy was obtained by the double glow plasma surface alloying technique. The structure and composition of the Mo–N modified Ti6Al4V alloy were investigated by X-ray diffraction (XRD) and glow discharge optical emission spectroscopy (GDOES). The surface-modified layer contains a Mo–N coating in the subsurface and a diffusion layer between the subsurface and substrate. The X‐ray diffraction analysis reveals that the outmost surface of the Mo–N modified Ti6Al4V alloy is composed of Mo2N. The friction and wear behaviors of the Mo–N modified Ti6Al4V alloy sliding against corundum balls in Hanks' solution were investigated and compared with that of Ti6Al4V alloy. The results show that the Mo–N modified Ti6Al4V alloy has better friction reduction and higher wear resistance properties than that of untreated Ti6Al4V.