International Journal of Surface Science and Engineering (12 papers in press)
Corrosion and passive film study of Cermet-coatings deposited by high-velocity oxygen fuel method in an acidic environment
by Akbar Niaz
Abstract: Cermet coatings are used for wear resistance applications, and it is generally understood that deterioration predominantly occurs due to frictional and erosion forces between two parts of mediums. The electrochemical corrosion of the Cermet coating is partially studied. The focus of the present work is on the detailed electrochemical corrosion study of WCCoCr coatings. The mild steel samples surfaces were cleaned by sandblasting before depositing multi-layers of coatings carried out by the high-velocity oxygen fuel method. The electrochemical corrosion testing was carried out by recording potential vs. time curves, potentiodynamic polarization, and impedance spectroscopy. The formation of oxides in the air and as a function of increasing voltage is studied by X-ray photoelectron spectroscopy. Our experimental results revealed that under stagnant conditions, electrochemical properties significantly change with time. The coating deterioration is expected to be worse in dynamic conditions where coatings surfaces are renewed by rubbing, sliding, or erosion conditions.
Keywords: Cermet coatings; Electrochemical testing; Corrosion degradation; Impedance spectroscopy; Coating passivation; Oxides characterization; WCCoCr coatings.
LONG-TERM WEAR PREDICTION OF ZIRCONIA ON ALUMINA CERAMIC FOR HIP PROSTHESIS
by Shankar Subramaniam, Nithyaprakash R, Sugunesh A.P, Uddin M.S
Abstract: This paper aims to predict wear of hard zirconia-on-hard alumina ceramic hip bearing couple for 20 years of lifetime by considering a realistic wear coefficient. Past studies in hip wear prediction have considered a fixed wear coefficient determined for a shorter sliding distance and used this for long-term wear prediction. In this study, pin-on-disc test between the zirconia and alumina bearing materials for a sliding distance of 60 km has been conducted in a dry and lubrication condition to determine friction and wear coefficient for initial running-in and subsequent steady-states. Finite element method has been employed to compute cumulative linear and volumetric wear of implant for 20 million cycles using the calculated wear coefficient values. Wear prediction showed lesser cumulative linear and volumetric wear for steady state wear coefficient when compared with running-in wear coefficient.
Keywords: Alumina; Zirconia; Wear Coefficient; Hip Prosthesis; FEM; Wear.
Quantitative assessment of the causes of the strengthening of a machined surface after cutting
by Alexey Popov, Sergei Babak
Abstract: Plastic deformation of the surface layer as a result of metal cutting leads to strengthening, i.e., to a change in the mechanical properties of the machined surface material. The strengthening of the surface layer of manufactured machine parts directly affects the life cycle of the finished product. This study focuses on the quality management of the machined surface after planing and face milling of structural and stainless steels. At the laboratory of the Department of Machining and Assembly of the Technical University of Liberec, experiments were conducted to quantitatively assess the causes in strengthening of the machined surface after cutting. The purpose of this study was to identify the strengthening degree of the machined surface due to processes occurring in the chip formation zone and on the rear surface of the cutting tool. This study has, for the first time, produced a quantitative assessment of the causes for the increase in microhardness as a result of the force during the passing of the future surface layer through the plastic deformation area that develops in the chip formation zone and the plastic deformation produced by the impact of the rear surface of the cutting tool on the machined surface.
Keywords: cutting; microhardness; plastic deformation; roughness; surface integrity.
Investigation UV-Treatment and Surface Modifications Effect on Surface Energy and Aging Behavior of Biomedical Surfaces
by Asli Gunay Bulutsuz
Abstract: Biomedical Ti6Al4V Eli alloy discs were subjected to blasting, anodization and Ultra-Viola (UV) treatments under the same manufacturing conditions with implants. These different surface modification effect on topography and wetting performance was investigated in detail with optical tensiometer for autoclaved and non-autoclaved samples. Surface contact angle changes after packing of the surfaces were investigated for initial, 1 and 3 months later. The topographical investigation by scanning electron microscope (SEM) showed that Blasted 350 V had the mean 1842
Keywords: Ultra-Viola Treatment (UV Treatment); Anodization; Autoclaving; Contact Angle; Aging Behavior; Implants.
Improvement in the Performance of Journal Bearings by Using Lead-free Bearing Material and Surface Texturing
by Vipin Kumar Sharma, Ramesh Chandra Singh, Rajiv Chaudhary
Abstract: The lead contents in the journal bearing material provide the antifriction and anti-wear properties. However, the lead element has some serious effects on the environment. By considering the harmful effects of the lead, two lead-free bearing material has been proposed in the present work. Aluminium-Nickel-Copper (Al-C) and Phosphorous-Aluminium-Copper (Ph-C) materials were fabricated using the stir casting technique. The wear and frictional properties of the fabricated material were evaluated with the help of a pin on disc setup with fully flooded, starved and unlubricated conditions. Apart from this, surface texturing on the interior surface of the bearing was also utilized to further improve the frictional behavior of the bearing. From the experimental results, it was revealed that Ph-C material exhibits the lowest amount of specific wear rate (SWR) and friction coefficient as compared to the conventional lead bronze (Pb-C) material. There was a 45-50 % improvement in SWR and 30-70 % improvement in frictional coefficient. For the journal bearing test experiments by considering the surface textures, there was an improvement in the average friction torque from textured bearing in the range of 2.7 % - 13.5 % compared to the non-textured bearing.
Keywords: Bearing material; wear; friction; material research; surface engineering; electric discharge machining.
INVESTIGATION ON SLURRY EROSION OF Al2O3 INCORPORATED GLASS/EPOXY COMPOSITES
by Ajith Joshi, M. Prasanna Kumar, Basavarajappas S
Abstract: The jet erosion of fiber reinforced plastics (FRPs) has been reported in many literatures available, but very few have reported on their slurry erosion behavior of FRPs. Furthermore, limited studies have paid attention on slurry erosion characterization of filler incorporated FRPs. Hence, present study was focused on slurry erosion behavior of alumina fillers incorporated glass/epoxy composites. The parameters considered were slurry concentration, contact angle and impact velocity. The experimental results reveal that increase in filler percentage increased the erosion resistance of glass/epoxy composites. The increase in slurry concentration and impact velocity has resulted in higher amount of erosion of studied composites. The material loss due to erosion increased with increase of impact angle till 45
Keywords: Slurry Erosion; Glass/Epoxy; Polymer Composites; Al2O3 filler;.
The Substrate Effect on Mechanical, Adhesion and Tribological Properties of CrCN Films Deposited by Magnetron Sputtering
by Aysenur Keles
Abstract: The service life of the machine parts is limited due to wear. For this reason, the process is done to protect the surface of the parts. Thin film coating is an application that only improves surface properties without changing the properties of the material. Transition metal nitrides are used in many areas from manufacturing to biomedical. CrCN films are metal nitrides with superior properties. The adhesion of the film to the substrate is important for the performance of the part as it will affect the surface properties. Therefore, the effect of substrate, an important parameter, was investigated in this study. CrCN films were coated onto M2, 4140, 316L and Ti6Al4V substrates using the pulsed-dc power supply by Closed Field Unbalanced Magnetron Sputtering (CFUBMS) technique. The microstructural properties of CrCN films were investigated using Scanning Electron Microscope (SEM). The phase orientation of CrCN films was determined by X-Ray Diffraction (XRD). The elemental composition and binding energy states of CrCN films were defined using X-ray Photoelectron Spectroscopy (XPS). A scratch tester was used to determine the adhesion between the coating and the substrate. Also, friction and wear properties were determined using a tribo-tester. The results showed that CrCN films had better adhesion to steel type substrates.
Keywords: CrCN; substrate; adhesion; magnetron sputtering; wear rate.
Enhanced Surface Properties of M2 Steel by Plasma Nitriding Pre-Treatment and Magnetron Sputtered TiN Coating
by M.S. Liborio, E.O. Almeida, S.M. Alves, R.R.M. Sousa, M.C. Feitor, T.H.C. Costa, R.M. Nascimento, M. Naeem, Mohsan Jelani
Abstract: AISI M2 high-speed steels are widely used in cutting/ forming tools due to their easy machinability and balanced toughness. Unfortunately, they exhibit severe cutting edge wear, which reduces their useful lifetime. The lifetime of such steels can be improved by titanium nitride (TiN) hard coating. However, in sliding wear applications having a metal-to-metal contact, such coatings exhibit low adhesion to the substrate due to substantial hardness differences among coating and substrate. Here, plasma nitriding is performed before the deposition of magnetron sputtered-TiN coating using various nitriding parameters to find whether the surface properties of the duplex treated sample can be altered by changing these parameters or not. It is found that the surface hardness and hardening depth can be improved by using the duplex treatment as compared to only TiN coating. The only coated sample exhibits? Ti?_4 N_2.33, ?Ti?_2 N phases, whereas duplex treated samples contain nitrogen-containing martensite phase, iron nitrides, and titanium nitride phases. A significant decrease in wear rate is attained using the duplex treatment and substantial improvement by altering the plasma nitriding parameters. This study suggests that plasma nitriding parameters affect the surface properties of duplex treated samples, and a fine-tuning of parameters is required to attain the best results, which we aim to investigate comprehensively in the future.
Keywords: M2 steel; TiN coating; Plasma nitriding; Magnetron sputtering; Wear resistance.
Activity modification of a new type of carbamide-based non-polluting solid powdery medium used in the sulphonitrocarburizing process
by Mihai Ovidiu Cojocaru, Mihai Branzei, Mariana Ion, Leontin Nicolae Druga
Abstract: Carbamide (technical grade urea) is frequently used as a highly efficient active component in the mediums used for ferritic or austenitic nitrocarburizing processes, and across a wide range of temperature values, ranging from values below 590 oC required for achieving the ferritic nitrocarburizing process, to values above 800
Keywords: carbamide; sulphonitrocarburizing; solid powdery medium; non-polluting medium; element potential.
Surface Microporous Formation on AISI 4140 Using Combination of Diffusion Treatment After Nitriding Gas in Muffle Reactor
by Komang Astana Widi, Wayan Sujana, Teguh Rahardjo
Abstract: Steel with microporous formation on surface layers is very important as self-lubricant and damping material. In this new method, AISI 4140 steel was subjected in two step combination treatment. First step is boost nitriding gas in fluidized bed reactor for 4 hours at 550 0C and the second step is diffusion nitriding gas for 2 h at 550 0C in muffle reactors. The diffusion without protective gas where air was present was applied after nitriding treatment in muffle reactors to release excess nitrogen which leads to microporous formation. This mechanism significantly increases surface porosity. The microporous formation at ε layer during diffusion at nitriding process is controlled by reaction formation of N2, NO, Cr2O3 and Fe2O3 which depends on the atmosphere condition in the muffle reactor. The dynamics of atoms during these formations create tensile and compressive stress in the grain boundary that increases porosity formation.
Keywords: microporous; self-lubricant; damping; diffusion; nitriding; muffle.
An assessment of erosive wear of hydro-turbine steel using statistical modeling and optimization
by Ishfaq Amin Maekai, G.A. Harmain
Abstract: The current study pertains to the influence of chosen process parameters on erosive wear of F6NM stainless steel. The sand used in the experimentation has been obtained from Dul-Hasti power plant dam site located in northern Himalayan rugged terrain of Jammu and Kashmir, India. Response surface methodology (RSM) was used to plan experiments. The wear experiments were conducted using slurry erosive wear tester (TR-40). Response surface method with face-centred composite design has been adopted to develop a regression model. Development of erosive wear model was based on five factors, which included sediment concentration (A), particle size (B), angle of impact (C), test duration (D) and rotational speed of slurry (E). Three levels were chosen for each factor considered in the study. A mathematical model was developed to predict the deterioration through wear on F6NM stainless steel and the appropriateness of the model was certified using analysis of variance. The developed regression model provides valuable information to control the damage (wear) and revealed that the rotational speed of slurry, particle size and sediment concentration were the three main contributing parameters for erosive wear of F6NM stainless steel. Rotational speed-sediment concentration was the main significant interactive pair. Subsequently, the damage model was developed based on the main contributory factors responsible for wear and significant interactions. The contribution of a rotational speed of slurry, particle size and sediment concentration was 30.58%, 18.82% and 17.64% respectively for an overall erosion wear process. A robust correlation is attained between the model predicted and experimentally obtained values for weight loss (response) and the percentage of error is 12%. On the basis of the mathematical model, single-objective optimization of operating parameters has been performed with genetic algorithm (GA) technique and this optimization method yields a reduction of 34.78% for material wear.
Keywords: Erosive Wear; Genetic Algorithm; Modeling; Optimization; Analysis of variance.
Root Cause Analysis of Pitting Corrosion of AA2024 and AA7075 after Exposure in Salt Fog Environment
by Pitichon Klomjit, Piya Khamsuk, Ekkarut Viyanit
Abstract: Two grades of anodized aerospace aluminum alloys, AA2024 and AA7075, were analyzed to determine root causes of pitting corrosion after the samples were exposed to a salt spray test according to ASTM B177. Methods to investigate pitting corrosion behavior of the aluminum alloys were divided into two steps: 1) characterization of pre-exposed (intact) anodized film and stimulated pitting corrosion by polarization and 2) comparison of samples that passed and failed the salt spray test. The surface properties were characterized by roughness measurements, scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy (EDS). Pitting corrosion was stimulated by potentiodynamic polarization prior to characterization of pitting by SEM and EDS to determine pitting initiation point. The results reveal that thickness of the film does not prevent localized corrosion. Cu-bearing intermetallic particles are detrimental to anodic film formation and cause pitting in the film. Potentiodynamic polarization tests alone cannot determine whether the film will pass or fail the salt spray test for 96 hours.
Keywords: anodized film; pitting corrosion; aluminum alloys; salt spary exposure; localized corrosion; intermetallic particles.