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Chen Y.,University of Windsor | Nie X.,University of Windsor | Leyland A.,University of Sheffield | Housden J.,Tecvac Ltd. | Matthews A.,University of Sheffield
Surface and Coatings Technology | Year: 2013

A cyclic inclined impact-sliding test was operated in an unlubricated, ambient environment and Hank's balanced salt solution (HBSS) to study the contact fatigue wear behavior of DLC and TiN biomedical coatings on relatively soft but corrosion resistant Ti alloy (Ti6Al4V) and hard but corrodible AISI M2 steel as model systems. The test was designed to simulate coating wear under combined impact and sliding motion. In each impact-sliding cycle, the forces comprised a dynamic impact load, Fi (140N) and a "pressing" load, Fp (300N). As expected, both coatings performed better on hard M2 substrates than Ti substrates under ambient test conditions. In the HBSS-lubricated solution test conditions, no obvious corrosion degradation occurred when either the bonding layers or substrates were Ti-based; instead, the solution provided a lubricating effect and enhanced coating performance. When the bonding layer for the DLC coating case was Si-based, it could not prevent crack propagation into the substrate after a certain number of test cycles. The crack opening allowed the HBSS solution to contact the substrates, which should only cause a minor problem when the substrate was a corrosion-resistant Ti alloy. However, when the substrate was corrodible M2, a severe corrosion-induced weakening of the interface occurred. When the coating bonding layer was a Ti layer (within the TiN coating), it could function to some extent as a corrosion and crack barrier to protect the M2 steel from interface degradation. Thus, a corrosion-resistant bonding layer and its ability to impede extension of cracking under cyclic dynamic loads can have a positive influence on the coating performance when the substrate has inferior anti-corrosion properties. © 2013 Elsevier B.V.


Llanes Leyva C.A.,Federal University of Minas Gerais | Godoy C.,Federal University of Minas Gerais | Bozzi A.C.,Federal University of Espirito Santo | Avelar-Batista Wilson J.C.,Tecvac Ltd.
Surface and Coatings Technology | Year: 2011

Ultra-low carbon (ULC) steels exhibit low yield strength and excellent formability. Plasma Assisted Physical Vapor Deposition (PAPVD) is a potential coating method for enhancing the strength at the surface of these steels [1]. However, when deposited onto low strength alloys PAPVD coatings may undergo premature failure if the substrate plastically deforms under heavy load. Extra load support is usually required for hard coatings to perform satisfactorily. Combined treatments involving plasma nitriding and PAPVD coating have been used to improve the load-bearing capacity of hard films [2]. This work describes the characterization and micro-abrasive wear behavior of Ti-stabilized ULC steels after surface modification by D.C Triode Plasma Nitriding (DC-TPN) and sequential coating with CrAlN by Electron Beam Plasma Assisted Physical Vapor Deposition (EB-PAPVD). Ti-ULC steel, plasma nitrided Ti-ULC steel and Ti-ULC duplex system were characterized by SEM, EDS, XRD analyses, micro-hardness and instrumented indentation hardness measurements, and stylus profilometry. Micro-abrasive wear tests were performed in fixed-ball configuration up to 1350 revolutions using SiC abrasive slurry and a 25mm diameter - AISI 52100 steel ball. Micro-abrasion mechanisms are presented and discussed. Nitrided steel and duplex systems were, respectively, 2.6 and 3.5 times harder than the untreated Ti-ULC steel. Wear coefficient of nitrided steel was 36% lower than that of the parent Ti-ULC steel. Regression analyses were used to calculate substrate (ks) and coating (kc) wear coefficients for the duplex system, the latter being 6.5 times lower than that of the nitrided steel. Coating thickness (3μm max.) was determined from inner and outer diameter measurements of the wear scars. Results indicate that it is feasible to manufacture duplex Ti-ULC steel via PAPVD, as significant improvements in wear resistance were recorded for both nitrided and duplex-treated steels. Duplex treatment clearly was the most effective method to enhance the wear resistance of ULC steels. © 2011 Elsevier B.V.


Wang L.,University of Windsor | Northwood D.O.,University of Windsor | Nie X.,University of Windsor | Housden J.,Tecvac Ltd. | And 3 more authors.
Journal of Power Sources | Year: 2010

In this study, the contact resistance (CR) and electrochemical properties of TiN, CrN and TiAlN electron beam physical vapor deposition (EBPVD) coatings and their stainless steel 316L (SS316L) substrate were investigated in a simulated proton exchange membrane (PEM) fuel cell environment. The potentiodynamic polarization corrosion tests were conducted at 70 °C in 1 M H2SO4 purged with either O2 or H2, and the potentiostatic corrosion tests were performed under both simulated cathodic (+0.6 V vs. Ag/AgCl reference electrode purged with O2) and anodic conditions (-0.1 V vs. Ag/AgCl reference electrode purged with H2) for a long period (4 h). SEM was used to observe the surface morphologies of the samples after corrosion testing. All the TiN-, TiAlN- and CrN-coated SS316L showed a lower CR than the uncoated SS316L. While the corrosion performance of the coatings was dependent on the cathodic and anodic conditions, the CrN coating exhibited a higher (in the anodic environment) or similar (in the cathodic environment) corrosion resistance to the uncoated SS316L. Thus, the CrN-coated SS316L could potentially be used as a bipolar plate material in the PEM fuel cell environment. Although the EBPVD process greatly reduced number of pinholes in the coatings compared to other plasma enhanced reactive evaporations, future research efforts should be directed to eliminate the pinholes in the coatings for long-term durability in fuel cell applications. © 2010 Elsevier B.V. All rights reserved.


Grant
Agency: Cordis | Branch: FP7 | Program: MC-ITN | Phase: FP7-PEOPLE-2011-ITN | Award Amount: 3.37M | Year: 2012

The main aim of the ENTICE proposal is to provide professional development in the multidisciplinary field of ENgineering Tribochemistry and Interfaces for IC Engines, capable to develop the new generation of clean and energy-efficient engines. It aims to train the next generation of researchers to work in diverse teams, to cross disciplinary and sectoral boundaries and apply advanced communication and information technologies to work across many scales of time and space. Detailed project objectives are: 1. To provide scientific and professional development to a highly motivated group of early stage researchers (ESRs) to address a number of key interdisciplinary research issues of great importance to the future of transport industries. 2. To facilitate and support scientific and professional development of two experienced researchers (ERs) to enable them to become the research leaders in two challenging interdisciplinary research areas. 3. To disseminate the knowledge and products developed through scientific research to industry, policy makers and the wider academic community for maximum impact of the research. 4. To initiate a sustainable long-term research, training and educational collaboration between the partners involved. Here we propose the development of a training network that brings together some of the key active research groups in Europe, with a leading international reputation, in complementary areas relevant to the fields of tribochemistry and interface design. A number of leading industrial companies, comprising of SMEs and LEs, will engage in training and facilitate the Transfer of Knowledge (ToK) to and from the industrial partner through research programmes for 12 ESRs and 2 ERs. The training programme proposed comprises two key elements; generic training to cover aspects of training required for future research leaders in academia and industry and on-the-job training which will include specialised project-specific skills and development.


Cassar G.,University of Sheffield | Avelar-Batista Wilson J.C.,Tecvac Ltd. | Banfield S.,University of Sheffield | Banfield S.,Tecvac Ltd. | And 4 more authors.
International Journal of Fatigue | Year: 2011

The effect of triode-plasma enhanced low-pressure oxygen and/or nitrogen diffusion treatments, either as a single process or in conjunction with plasma-assisted physical vapour deposition (PAPVD) on Ti-6Al-4V has been studied under rotating-bending fatigue testing. Following the diffusion treatment, samples exhibit a hardened case, more than 30 μm deep. Semi-logarithmic S-N plots are used to demonstrate and compare the significant changes in fatigue resistance obtained from each process. Fractography and residual stress measurements show that, compared to annealed samples, the fatigue strength of the diffusion-treated samples was superior; although the result changed depending on the processing parameters and microstructure of the substrate material. Also, unsupported and mechanically uncompliant ceramic coatings, such as TiN, promote the initiation of multiple crack sites, which lead to premature failure of the Ti-alloy substrate and a consequent reduction in endurance limit. © 2011 Elsevier Ltd. All rights reserved.

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