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2019 Industrial Lubrication and Tribology
This paper aims to investigate the structural, corrosion and the study of tribocorrosion features of the AA7075 aluminum alloy with and without the application of electroless Ni-P/Ni-B duplex coating with a thickness of approximately 40 microns.Design/methodology/approachSurface characterization of the samples was made by structural surveys (light optic microscope, scanning electron microscopic examinations and X-ray diffraction analyses), hardness measurements, corrosion and tribocorrosion tests.FindingsResults of the experiments showed that upper Ni-B coating deposited on the surface of first Ni-P layer by duplex treatment caused remarkable increment in the hardness, corrosion resistance and tribocorrosion performance as compared to the AA7075 aluminum alloy.Originality/valueThis study can be a practical reference and offers insight into the effects of duplex treating on the increase of hardness, corrosion and tribocorrosion performance.
Alhattab, Ali Abdul Munim; Dilawary, Shaikh Asad Ali; Motallebzadeh, Amir; Arisoy, Cevat Fahir; Cimenoglu, Huseyin
2019 Industrial Lubrication and Tribology
The purpose of this study is to investigate the effect of electron beam surface melting (EBSM) on the properties of Plasma Transfer Arc (PTA) deposited Stellite 12 hardfacing.Design/methodology/approachFor this purpose, structural characterization and dry sliding wear tests have been conducted on the hardfacings at room temperature. The wear tracks formed on the surfaces of the hardfacings were examined by a stylus-type profilometer and a scanning electron microscope.FindingsRefinement of the matrix and the carbides following EBSM process led to about 15 per cent increment in hardness as compared to PTA state. Despite an increase in the surface hardness, EBSM’ed hardfacing exhibited about 50 per cent lower sliding wear resistance than PTA hardfacing against alumina ball. According to the worn surface examinations, reduction in the wear resistance of Stellite 12 after EBSM process has been associated with the extensive refinement of the carbides which made them easier to be removed from the matrix during the sliding contact.Originality/valueThe authors of current study have applied EBSM to PTA deposited Stellite 12 hardfacing alloy to investigate if the surface structure and properties could be improved. More specifically the dry sliding wear performance of PTA and EBSM’ed hardfacings have been focused in the scope of this study. To the best of the authors’ knowledge, this approach, i.e. use of EBSM as a post deposition treatment of Stellite 12 hardfacings, has not been reported in open literature.
Demirtas, Selman; Kaleli, Hakan; Khadem, Mahdi; Kim, Dae-Eun
2019 Industrial Lubrication and Tribology
This study aims to investigate the tribological characteristics of a Napier-type second piston ring against a cylinder liner in the presence of graphene nano-additives mixed into 5W40 fully synthetic engine oil.Design/methodology/approachWear tests were carried out in the boundary lubrication condition using a reciprocating tribometer, and real engine tests were performed using a single spark ignition Honda GX 270 test engine for a duration of 75 h.FindingsThe experimental results of the tribometer tests revealed that the nano-additives formed a layer on the rubbed surfaces of both the piston ring and the cylinder liner. However, this layer was only formed at the top dead center of the cylinder liner during the engine tests. The accumulation of carbon (C) from the graphene was heavily detected on the rubbed surface of piston ring/cylinder liner, mixed with other additive elements such as Ca, Zn, S and P. Overall, the use of graphene nano-additives in engine oil was found to improve the frictional behavior in the boundary and mixed lubrication regimes. Abrasive wear was found to be the main mechanism occurring on the surface of both piston rings and cylinder liners.Originality/valueThough many researchers have discussed the potential benefits of graphene as a nano-additive in oil to reduce the friction and wear in laboratory tests using tribometers, to date, no actual engine tests have been performed. In this paper, both tribometer and real engine tests were performed on a piston ring and cylinder liner using a fully formulated oil with and without graphene nano-additives in the boundary lubrication condition. It was found that a graphene nano-additive plays an active role in lowering the coefficient of friction and increasing surface protection and lubrication by forming a protective layer on the rubbing surfaces.
Pourhashem, Sepideh; Rashidi, Alimorad; Vaezi, Mohammad Reza
2019 Industrial Lubrication and Tribology
In this research, the effect of graphene nanosheets and graphene quantum dots (GQDs) as carbon-based nanofillers on corrosion protection performance of epoxy coatings is considered.Design/methodology/approachGraphene nanosheets are synthesized via chemical vapor deposition method, and GQDs are synthesized by a simple and gram scale procedure from carbon black. The prepared nanofillers are characterized by X-ray diffraction technique, Fourier transform infrared spectroscopy and transmission electron microscopy. Further, solvent-based epoxy coatings containing 0.1 Wt.% graphene nanosheets and GQDs are prepared, and the corrosion resistance of nanocomposite coatings is considered by electrochemical impedance spectroscopy.FindingsThe results indicate that both epoxy/graphene nanosheets and epoxy/GQDs samples have significantly higher corrosion resistance than pure epoxy coating. Meanwhile, GQDs can more effectively enhance the corrosion protection performance of epoxy coatings compared to graphene sheets, which can be attributed to the presence of functional groups on GQDs and improving the dispersion quality in polymer matrice.Originality/valueIn this research, for the first time, the graphene quantum dots (GQDs) prepared by a “top-down” method from carbon black are used as nanofiller in epoxy coatings, and the potential application of graphene nanosheets and GQDs as anti-corrosion nanofiller in epoxy coatings is investigated.
Tian, Zaihao; Ma, Jin-Kui; Changhou, Lu; Chen, Shu-Jiang
2019 Industrial Lubrication and Tribology
The purpose of this paper is to maximize the load-carrying capacity (LCC) of a rotating ring, a numerical model optimizing both the surface and bottom shape of its surface textures is proposed.Design/methodology/approachThe Reynolds equation is used to evaluate the film pressure and LCC obtained by integrating the film pressure is set as the objective function. Around the center of the computational domain, radial lines with an equal angle between adjacent ones are produced and the surface contour of textures is obtained by connecting the endpoints using a spline curve. The bottom profile is then obtained by connecting the endpoints of two vertical lines at the circumferential ends of textures. Lengths of these lines are set as design variables and genetic algorithm is used to solve optimization models.FindingsResults show that optimum textures have an “apple-like” surface contour and a “wedge-like” bottom profile, which are both expressed by smooth spline curves. Optimum wedge-bottom textures generate higher LCC than optimum flat-bottom textures. Moreover, the optimum textures have the highest LCC compared with optimum grooves proposed previously, which validates the practical value of the current optimization model.Originality/valueThis work presents a comprehensive optimization method of texture geometry, which provides a new idea of the design of surface textures.
Zhang, Fuying; Shui, Hao Che; Zhang, Yufei
2019 Industrial Lubrication and Tribology
The purpose of this paper is based on the response surface method, the authors determined the conditions for achieving the optimum rubber-sealing performance by using the maximum contact stress as the response value.Design/methodology/approachA two-dimensional model of a compression packer rubber was established by finite-element analysis software. Under the single axial load of 53.85 MPa, the four single factors of the end-face inclination angle, subthickness, height of rubber and friction coefficient of the rubber were analyzed.FindingsResults show that the optimum sealing performance of the rubber tube is achieved when the end-face angle is equal to 45º and the thickness of the rubber tube is 9 mm. The response surface designed by Box–Behnken shows that the sealing performance of the rubber tube is the optimum when the end-face inclination angle is 48.1818°, the subthickness is 9 mm, the height of rubber is 90 mm and the friction coefficient is 0.1. Verification test results show that the model is reliable and effective.Originality/valuePacker operations are performed downhole, and research on real experiments is limited. In this work, the feasibility of such experiments is determined by comparing finite-element modeling with actual experiments, and the results have guiding significance for actual downhole operations.
Wang, Xingjun; Yang, Zhuoran; Xu, Feifei; Wang, Liping
2019 Industrial Lubrication and Tribology
The microcutting performance of the 10B/Al composite is significantly poor because of the existence of hard boron particles. The effects of cutting parameters, including uncut chip thickness and cutting speed, on the material removal mechanism and surface generation are investigated to improve the surface quality.Design/methodology/approachThe 2D finite element model, which includes a rigid cutting tool, a reinforced phase, a matrix and a dense layer, is established. The effects of uncut chip thickness on material removal mechanism and surface generation are analyzed from a probabilistic perspective. The relationship between the uncut chip thickness and the probability in which the machined surface will have a better surface quality is constructed. A Gaussian distribution formula is applied to describe the machined surface quality.FindingsTwo representative particle-removal modes, namely, cutting-through and pulling-out modes, are observed. For cutting-through mode, when the relative cutting location is small, better surface quality is obtained. For pulling-out mode, the quality of the machined surface gradually improves because the further increase of the relative cutting location reduces the height of the generated pit and scratches. The microcutting at high cutting speed tends to suppress the scratch phenomenon. The best surface quality will be obtained at small uncut chip thickness and high cutting speed.Originality/valueThe surface quality generated in microcutting of the 10B/Al composite can be improved by optimizing the cutting parameters and controlling the particle-removal modes based on the proposed Gaussian distribution formula.
2019 Industrial Lubrication and Tribology
The purpose of this paper is to investigate the effect of the rounding in bump foil on the static performance of air foil journal bearings.Design/methodology/approachDuring the study, the bending moment of the new foil structure with rounding is proposed, and the bump foil stiffness is obtained from the elastic deformation energy theory. The validity of the presented foil model is verified through comparison with previous models. The static characteristics of foil bearings such as film thickness and attitude angle are obtained using a fully coupled elastic-gas algorithm and are compared to models with various rounding radius and friction coefficients.FindingsThere is an optimal rounding radius that makes the stiffness of bump foil maximum. As the static load increases, the minimum film thickness is proportional to the rounding radius but the attitude angle is inversely proportional. The effect of rounding with a large friction coefficient becomes negligible.Originality/valueThe rounding brings fundamental difference in the structural stiffness and static performance of foil bearings. The results are expected to be helpful to bearing designers, researchers and academicians concerned.
Liu, Lei; Xu, Zongwei; Tian, Dongyu; Hartmaier, Alexander; Luo, Xichun; Zhang, Junjie; Nordlund, Kai; Fang, Fengzhou
2019 Industrial Lubrication and Tribology
This paper aims to reveal the mechanism for improving ductile machinability of 3C-silicon carbide (SiC) and associated cutting mechanism in stress-assisted nanometric cutting.Design/methodology/approachMolecular dynamics simulation of nano-cutting 3C-SiC is carried out in this paper. The following two scenarios are considered: normal nanometric cutting of 3C-SiC; and stress-assisted nanometric cutting of 3C-SiC for comparison. Chip formation, phase transformation, dislocation activities and shear strain during nanometric cutting are analyzed.FindingsNegative rake angle can produce necessary hydrostatic stress to achieve ductile removal by the extrusion in ductile regime machining. In ductile-brittle transition, deformation mechanism of 3C-SiC is combination of plastic deformation dominated by dislocation activities and localization of shear deformation. When cutting depth is greater than 10 nm, material removal is mainly achieved by shear. Stress-assisted machining can lead to better quality of machined surface. However, there is a threshold for the applied stress to fully gain advantages offered by stress-assisted machining. Stress-assisted machining further enhances plastic deformation ability through the active dislocations’ movements.Originality/valueThis work describes a stress-assisted machining method for improving the surface quality, which could improve 3C-SiC ductile machining ability.
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