International Journal of Surface Science and Engineering (19 papers in press)
Combined influence of couple stress lubricant and geometric imperfections of journal on the performance of membrane compensated two-lobe hybrid journal bearing
by Dharmendra Jain, Stish C. Sharma
Abstract: This paper deals with the comparative performance of the two-lobe and circular hybrid journal bearing systems compensated with membrane restrictor. The combined influence of geometric imperfection of journal and the couple stress behavior of the lubricant has been taken into the consideration. The non-Newtonian behavior of the lubricant has been modeled using Stokes couple stress fluid model. The Reynolds equation has been modified to consider the couple stress fluid behavior and has been solved by the FE Galerkins approach. The numerically computed results from present study indicates that the couple stress lubricant presents an improved bearing performance in terms of stability(threshold speed), fluid film stiffness and damping coefficients vis-
Keywords: two-lobe bearing; geometric imperfection; couple stress fluid; FEM.
HFCVD nanostructured diamond films deposited by a combination of seeding suspensions and novel nucleation process (NNP)
by Debarati Mukherjee, Riccardo Polini, Veronica Valentini, Shlomo Z. Rotter, Joana C. Mendes
Abstract: The deposition of thin diamond films on foreign substrates requires the ultrasonic treatment of the substrate with diamond suspensions. This procedure leaves nanometre-sized seeds on the substrate surface; the seeds coalesce and form a closed conformal film during early stages of diamond growth. To get insight on seeds early growth and to evaluate the seeding efficiency of different suspensions, silicon samples were placed inside a HFCVD system and half of each sample was exposed to diamond growth conditions; this pre-treatment leaves a thin carbon film on the surface of the exposed regions. Following this step samples were seeded with commercially available nanodiamond suspensions and exposed again to growth conditions. Finally, samples were characterized by SEM. Results showed that seeding suspensions played a role depending on particle size and nature of dispersing medium. The growth mode on pre-treated regions showed distinct features, in particular a larger seeding density and a more uniform distribution of nanoseeds. As a consequence, continuous films formed more quickly on these regions. The carbon film deposited before the seeding step improves deagglomeration of nanodiamond seeds via a more effective interaction between substrate surface and seeds. Therefore, this procedure represents a viable way to grow thin conformal diamond coatings by HFCVD.
Keywords: HFCVD; novel nucleation process (NNP); nanodiamond; seeding.
Analysis of oxide scale deformation and surface roughness characterisation in hot rolling of stainless steels
by Xiawei Cheng, Dongbin Wei, Zhengyi Jiang, Laizhu Jiang
Abstract: Stainless steels are iron-based alloys that contain a minimum of about 12% Cr. They have been classified by microstructure at room temperature, e.g., austenitic stainless steel grade 304 and martensitic stainless steel grade 410L. The quality of the finished product is significantly affected by the deformation of the oxide scale and its surface roughness characterisation in hot rolling of stainless steels. Two stainless steel grades 304 and 410L were studied in this paper. Hot rolling was performed on a Hille 100 experimental rolling mill under various reductions between 10 and 40% with consideration of the oxide scale thickness controlled by oxidation time. Oxide scale thickness and microstructures were analysed using scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). The experimental results show that the deformation behaviour of the oxide scale on the stainless steel 304 is sensitive to its thickness and exhibits higher resistance to be deformed. However, the reduction in thickness plays an important role in the uniformity of the oxide scale deformation for the stainless steel 410L. Friction coefficients were calculated and compared under different rolling parameters. Simulations results show that the reduction in thickness and initial surface roughness play roles on final surface roughness. Steel substrate surface is rougher than that of the oxide scale at different reductions.
Keywords: stainless steel; oxide scale; deformation; friction; surface roughness.
Wear study of coatings obtained using different parameters of thermal spraying
by Regita Bendikiene, Tilmute Pilkaite, Liudas Albinas Kuliavas
Abstract: Understanding the feedstock material behaviour in thermal spraying process under different parameters is a key factor in producing repeatable and controllable coatings. This article reviews three different technological regimes of thermal spraying process, with a particular focus on the wear behaviour under the different conditions of obtained coatings. Commercial RocDur 37 flexi cord was selected as feedstock material. A buffer bond layer was used to ensure proper adhesion of coating to substrate material. Three technological regimes applying different longitudinal feed of torch were conducted in the work presented: 1.43 cm/s (A), 1.85 cm/s (B), 0.88 cm/s (C); and different number of torch passes: 6 (A), 4 (B), and 11 (C) respectively. Rotation speed of the device in each of the regimes was the same 1.33 s-1. In order to evaluate application of coatings in the different exploitation conditions the wear behaviour of thermal sprayed coatings was tested on the contact sliding, edge wear and abrasive wear testing machines. Technological regimes B and C showed better wear performance particularly in contact sliding and edge wear tests. Hydro abrasive wear test results showed very similar wear performance of coatings obtained using three different technological parameters (A, B, C), therefore it can be concluded that RocDur 37 flexi cord coatings are suitable for work in abrasive wear conditions. In this type of wear technological parameters do not affect wear behaviour of coatings. The optimum technological regimes were defined: rotation speed 1.33 s-1, longitudinal feed 0.88 cm/s, and 11 torch passes.
Keywords: thermal spraying; wear resistance; flexi cord feedstock; wear test.
High Temperature Tribological Characterization of Laser Surface Melted Ni-based Superalloy
by V. Dillibabu, Duraiselvam Muthukannan, Muhammed Anaz Khan, K.P. Naveena
Abstract: Laser surface treatment was performed on nickel-based superalloy to improve their high temperature tribological properties for enhanced service life specifically in gas turbine applications. The laser power and scan speed were strategically controlled to optimally refine the microstructure. The metallurgical and mechanical modifications in the treated area were studied to understand the refining mechanism. The coarser grains in the base material reorient to fine dendrites during laser surface melting. The equiaxed grains are refined with increased laser power and reduced interaction time under the influence of higher cooling rate. The finely refined grains improve the microhardness of the treated surface. The tribological performance and its mechanism of the treated surfaces were evaluated at room temperature and at 500
Keywords: Laser surface melting; Ni-superalloy; High temperature; Wear.
Relative anti-wear property evaluation of nano garnet gear lubricant
by MAHESWARAN R, Sunil J
Abstract: In gear boxes, the life of gears is increased by reducing the wear caused due to the friction between the rubbing surfaces of gears. This paper addresses on the study of the relative anti-wear property of nano garnet gear lubricant which are formulated by dispersing 0.25 wt%, and 0.50 wt% of nano garnet particles in commercially available SN500 grade gear lubricant oil through a standard two-step method. The anti-wear property of the lubricant is estimated by a Four-ball wear test and is measured through the microscopic investigations on the surface texture modifications namely width of the wear ring and wear scar diameter. The width of wear ring is reduced to 3.83%, 6.39%, and the wear scar diameter is reduced to 6.1%, 2.44% due to the addition of 0.25 wt%, and 0.50 wt% of particle concentrations at a maximum applied load of 588N due to the rolling effect of nano garnet particles.
Keywords: lubricant; anti-wear; surface texture modification; Four-ball wear test; wear ring; wear scar.
Study of annular recess hydrostatic tilted thrust pad bearing under the influence of couple stress lubricant behaviour
by Vivek Kumar, Satish C. Sharma
Abstract: This paper concerns with the theoretical investigation to predict the combined influence of couple stress lubricant and tilt between bearing pad surfaces, on the performance of externally pressurized annular recess thrust pad bearing. Stokes micro-continuum theory is used to derive modified Reynolds equation accounting for the presence of couple stress additives in lubricant. A MATLAB code has been developed to solve the governing equation using FEM technique. Influence of annular recess location and tilt between pad surfaces are investigated on the performance of hydrostatic thrust pad bearing. It has been observed that the use of couple stress lubricant significantly improves the performance of annular recessed hydrostatic thrust pad bearing. Presence of tilt between bearing surfaces proved to be beneficial in terms of dynamic characteristics of bearing system.
Keywords: Hydrostatic tilted thrust pad bearing; Annular recess; Couple stress lubricant; FEM Technique.
The effect of substrate bias voltage on the adhesion strength of ta-C coated tools prepare by filtered cathode vacuum arc
by Young-Jun Jang, Yong-Jin Kang, Jong-Kuk Kim
Abstract: Filtered cathode vacuum arc (FCVA)-deposited ta-C coating have found application for cutting tools. In this study, the effect of bias voltage on the physical properties of the coating and cutting performance were experimentally investigated. A bias voltages were applied with 0, 75, 150, 300 V and thicknesses were fixed with 430 nm. The experimental results showed that the regardless of the bias voltage, the adhesion strength indicates that all ta-C coating were HF 1 level. However, increasing substrate bias voltage will increase the C=C boning at the ta-C coating, especially 150 and 300 V. Moreover, hardness values also decreased with increased bias voltage. For the cutting test, a selected the ta-C coating from the lowest I(D)/I(G) value (0.5) with 75 V bias condition. After cutting test, the adhesive of Al debris and delamination on the ta-C coated surface was 3 times lower than commercial DLC. This phenomenon summarized that heat resistance of ta-C coating is dominant with high portion of sp3 fraction.
Keywords: tetrahedral amorphous carbon (ta-C); FCVA; Adhesion; cutting tool; Raman.
Correlation between 3D Fractal Dimension and Abrasive Wear Resistance
by Abdeljalil Jourani
Abstract: Fractal theory is usually used to investigate the topography of machined surfaces, but the relationship between fractal dimensions and wear rate is less studied. A contribution in this field is proposed with wear tests performed on the AISI 1046 steel after the grinding by use of the P80, P180 and P320 abrasive sheets. A 3D fractal study of the worn surfaces is carried out by using power spectral density (PSD) in order to examine the relationship between rate of wear and its 3D fractal dimension. The 3D fractal analysis of the worn surfaces showed that higher values of fractal dimensions indicate a larger real contact area and therefore a better wear resistance of the AISI 1046 steel.
Keywords: wear; friction; surface topography; surface roughness; 3D fractal dimension.
3D inspection technology combining passive stereo matching and active structured light for steel plate surface sample
by Xin Wen, Kechen Song, Menghui Niu, Zhipeng Dong, Yunhui Yan
Abstract: Three-dimensional (3D) inspection technology is a new important research hotspot in the field of steel surface defect inspection. However, current 3D information acquisition methods (i.e., the passive stereo vision method and active structured light method) still suffer from several issues. In order to solve these issues, a three-dimensional inspection system is designed in this paper. In this system, the passive stereo vision method and active structured light method are combined to obtain the surface sample height information of high temperature steel plate. Furthermore, the Hg_Census (Hexagonal grid Census) transform is proposed to improve the robustness of census transform stereo matching. Moreover, the passive stereo disparity map is adopted as a constraint condition to realize phase matching using wrapped phase. In addition, the local phase matching and sub-pixel disparity refinement are proposed to obtain high measuring accuracy. Three high temperature steel plate surface samples are picked to verify the effectiveness of the proposed method. The actual experimental results present the average error is less than 1 mm.
Keywords: surface sample height; three-dimensional inspection; stereo vision; active structured light.
SLIDING WEAR OF AISI1040 STEEL AT DIFFERENT THERMO CHEMICAL SURFACE TREATED CONDITIONS
by A. Arulbrittoraj, P. Padmanabhan, M. DuraiSelvam
Abstract: This work aims to investigate the sliding wear of pack borided AISI1040steel, carried out at 1000C for 12hours with Na2B4O710H2O as low potential born source, using pin-on-disc apparatus as function of applied load and sliding distance at the sliding speed kept constant; compared with gas carburized samples carried at 930
Keywords: Boriding; Carburizing; Wear rate; Wear coefficient; Frictional forces.
Investigation of the Tribological Behavior of Electrocodeposited Ni-MoS2 Composite Coatings
by Ebru Saraloğlu Güler, Erkan Konca, İshak Karakaya
Abstract: Composite electroplating of solid lubricants in a metal matrix is an effective way to lower coefficient of friction (COF) and improve wear resistance of surfaces in sliding contact. In this work, NiMoS2 composite coatings were deposited on AISI 304 stainless steel substrates by electroplating from Watts bath containing suspended MoS2 particles and their tribological behavior was studied. The effects of MoS2 particle concentration (5, 10 and 30 g/l), MoS2 particle size (1.440 and 5.156
Keywords: electrocodeposition; MoS2 particle; friction; wear; surfactant; sodiumlignosulfonate.
Experimental investigation on wear characteristics of sintered Fe-C-Cr low alloy steels
by Kandavel T.K., Panneerselvam T, Vignesh Mohan
Abstract: Wear is a common property exhibited when two materials rub against each other. The present research work aims to investigate the influence of chromium (Cr) on wear characteristics of powder metallurgy (P/M) plain carbon steel (Fe-0.5%C) and to find optimal parameters for minimum wear loss and frictional coefficient of the P/M alloy steels. The sintered-forged plain carbon steel and with addition of 1% and 2% Cr P/M alloy steels were made into cylindrical pins to conduct wear tests as per the standard. The Design Expert (DE) software was used for conducting the dry sliding wear tests. Addition of Cr reduces the mass loss due to the formation of chromium carbides embedded in the ferrite grain matrix in the microstructure. The optimum working parameters found for the minimum mass loss and coefficient of friction from the Taguchi-grey relational analysis are 50N load and 113.5rpm speed irrespective of the alloy steels.
Keywords: sintering; chromium; wear; microstructure; SEM; optimization; Taguchi method.
The evaluation of lubricant properties and environmental effect of Bio-lubricant developed from Rice Bran Oil
by S. Rani
Abstract: This paper deals with the comparison of lubricant properties and environmental effect of newly developed bio-lubricant based on rice bran oil. The various lubricant properties like rheological, tribological, thermal properties, oxidative stability, corrosive stability, biodegradability and toxicity of the formulated oil have been evaluated and compared with a commercially available lubricant SAE 20W40. The formulated oil from rice bran oil is found to be highly biodegradable, less corrosive and non-toxic. Even though the coefficient of friction of the formulated oil is less compared to SAE 20W40, the wear scar diameter is slightly high compared to SAE 20W40.
Keywords: Rice bran oil; bio-lubricants; non-toxic; biodegradability; Zebra fish.
Enhancement of Surface Properties of Nanocrystalline TiN Coated Plasma Nitrided AISI 310 Austenitic Stainless Steel
by Pankaj Singh, Arbind Kumar, Sanjay Sinha, Aman Aggarwal, Gajendra Singh
Abstract: The surface modification with combination of plasma nitriding and TiN coating on 310 stainless steel significantly improved the surface hardness and corrosion properties. X-ray diffraction (XRD) showed the expanded austenite, CrN and TiN phases along with austenite phase. The nitrided layer in the range of 10-50
Keywords: Austenitic steel; Plasma Nitriding; TiN; Corrosion; Hardness; ICR.
Evaluation of effective models of offset CtP plate aluminum oxide surface roughness characterization
by Zivko Pavlovic, Sandra Dedijer, Nemanja Kašiković, Dragoljub Novaković, Magdolna Pál (Apro), Dubravko Risović
Abstract: In this study, three different approaches for characterization of printing plates non-printing elements surface structure and roughness were compared: stylus profilometric method, AFM, method and software (indirect), SEM image based profilometry. The comparison was made to evaluate the possibility of utilising the different methods for characterization of CtP offset printing plate surface roughness. The direct profilometric measurements involved the use of stylus profilometer visual analysis were made using AFM device and for indirect approach the Gwyddion software, for analysis of single and stereo SEM images and calculation of standard profilometric parameters, was used. The results of this study demonstrate that it is possible to obtain profilometric parameters from the analysis of AFM and SEM micrographs with appropriately calibrated grey scale intensity distribution and that the values of the parameters are comparable to those obtained by contact stylus profilometry. The results of this comparative study indicate that profilometric 2-D direct stylus method is more applicable when larger areas tend to be measured, while the indirect image-based 3-D profilometry is a valuable and efficient tool for characterization of various surface's topographies on micron scale sample areas.
Keywords: contact stylus profilometry; surface roughness; surface topography; AFM; SEM micrograph; printing plate; aluminium oxide.
Mechanical responses of coated solids in elastohydrodynamically lubricated line contacts
by Yangyi Xiao, Wankai Shi, Jing Luo
Abstract: For layered solids consisting of physical vapor deposition coatings on steel substrates in lubricated line contacts, the elastohydrodynamic lubrication (EHL) behavior is studied by the full-system finite element approach. Numerical solutions illustrate that the coating thickness, elastic modulus, and operating conditions have significant influences upon the EHL film pressure and thickness profiles, along with the coefficient of friction. Results for stress distributions provide insight into the tendency for yielding, pitting, and interfacial delamination in coated bodies. Furthermore, the film pressure and stress status induced by the interfacial micro-valley as well as rough coating surface and interface are investigated. It is demonstrated that optimized multi-layer coatings are propitious to reduce the stress gradient and failure risks of coated materials.
Keywords: Elastohydrodynamic lubrication (EHL); Coating; Multi-layer; Mechanical response.
Effect of Process Parameters on the Microstructure, Hardness and Wear Resistance Properties of Zn-Sn-Ti Coatings on AISI 1015 Steel: Laser Alloying Technique
by OLAWALE FATOBA, ESTHER AKINLABI, ELIZABETH MAKHATHA
Abstract: The deterioration of materials during industrial application poses a serious threat to the materials structural integrity. A materials susceptibility to wear and surface damage can be reduced by alteration of its surface chemistry, morphology and crystal structure. Therefore, modification of surface properties plays an important role in optimizing a materials performance for a given application. The aim of the research was to investigate the enhancement in the microstructure and wear properties of Zn-Sn-Ti ternary coatings on AISI 1015 steel by laser alloying technique using Ytterbium Laser System (YLS). A laser power of 750-900 W, scanning speeds of 0.6 and 0.8 m/min, and alloy compositions of 25Zn-25Sn-50Ti and 20Zn-20Sn-60Ti were used in this study. Increase in Ti content from 50 to 60% at different laser processing conditions resulted in improved properties. The enhanced properties were obtained at 20Zn-20Sn-60Ti alloy at laser power of 950 W and speed of 0.8 m/min. At optimum composition and speed of 0.8 m/min, there was enhancement of 24% in wear resistance performance. In addendum, significant reduction in wear volume loss of 20Zn-20Sn-60Ti alloy at 0.8 m/min was attributed to excellent wear resistance performance due to metastable intermetallic phases. The coatings were free of cracks and pores with homogeneous and refined microstructures with good adhesion to the substrate. Iron content in the substrate modified the intermetallic compounds and the enhanced wear resistance performances of Zn-Sn-Ti ternary coatings can be attributed to major hard phases of iron-titanium (Fe2Ti), iron-zinc (FeZn6.67, FeZn15), iron-tin (FeSn2), and titanium-zinc (TiZn16) intermetallic compounds and high hardness and strong covalent dominant atomic bonds. Response Surface Model (RSM) used in this research authenticates reasonably with the experimental results.
Keywords: AISI 1015; Zn-Sn-Ti coatings; wear resistance; hardness; microstructure; Response Surface Model (RSM).
Neural network modelling of Abbott-Firestone roughness parameters in honing processes
by Maurici Sivatte-Adroer, Irene Buj-Corral, Xavier Llanas-Parra
Abstract: In present study, three roughness parameters defined in the Abbott-Firestone or bearing area curve, Rk, Rpk and Rvk, were modeled for rough honing processes by means of Artificial Neural Networks (ANN). Input variables were grain size and density of abrasive, pressure of abrasive stones on the workpiece’s surface, tangential or rotation speed of the workpiece and linear speed of the honing head. A back propagation algorithm was used for training the networks. Two strategies were considered, use of either one network for modeling the three parameters at the same time and use of three networks, one for each parameter. Best network was chosen among different structures, having either one or two hidden layers. Overall best neural network consists of three networks, one for each roughness parameter, with one hidden layer having 25, 9 and 5 neurons for Rk, Rpk and Rvk respectively. However, use of one network for the three roughness parameters would allow addressing an indirect model. In this case, best solution corresponds to two hidden layers having 26 and 11 neurons.
Keywords: Roughness; honing; artificial neural networks; neurons; back propagation algorithm; grain size; density of abrasive; linear speed; tangential speed; pressure.