M.A. Fazal

Laser-based Surface Modifications of Aluminum and its Alloys

Aluminum (Al) and its alloys have widespread engineering applications because of their higher strength to weight ratio, ductility, and formability. However, in various applications, mechanical properties such as hardness, corrosion, wear, and fatigue resistance are prerequisite at near surface regions. Such localized modification without affecting the bulk phase can be performed by various surface-engineering approaches including electro-deposition, physical and chemical vapor depositions, thermal spraying, plasma spraying, and organic polymeric coatings. Delamination failure of such coatings from the substrate is often inevitable due to the difference in film-to-substrate elastic modulus associated with the aforementioned processes. Recently, researchers have adopted a new approach of laser surface engineering to modify the near surface regions of metallic substrate by laser beams resulting in superior mechanical properties with the formation of novel microstructures. In this article, the recent developments in the surface modification of Al and its alloy by laser treatment are reviewed. Processing parameters and resulting microstructures of Al and its alloys are briefly summarized, along with their impact on mechanical properties. Finally, this article concludes future research directions.

Effect of rare earth elements and their oxides on tribo-mechanical performance of laser claddings: A review

Laser cladding is a promising photon-based surface engineering technique broadly utilized for fabricating harder and wear resistant composite coatings. In spite of excellent properties, the practical applications of laser claddings are relatively restricted when compared with well-established coating techniques because of their inherent defects identified as cracks, pores and inclusions. Substantial evidence suggests that the incorporation of an appropriate amount of rare earth in laser claddings can remarkably prevent these defects. Additionally, the presence of rare earth in laser claddings can notably enhance tribo-mechanical properties such as surface hardness, modulus of elasticity, fracture toughness, friction coefficient and wear rate. In this literature review, the effect of rare earth in reducing dilution and cracks susceptibility of laser claddings in addition to microstructural refinement attained was examined. Mechanical and tribological properties of these claddings along with their underlying mechanism were discussed in detail. Finally, this article summarizes current applications of laser claddings based on rare earth and was concluded with future research directions.

Effect of corrosion inhibitors on corrosiveness of palm biodiesel

Abstract The present study aims to investigate the effect of two organic corrosion inhibitors, i.e. benzotriazole and adenine on the corrosion behaviour of copper and mild steel upon exposure to palm biodiesel. Static immersion tests were conducted by exposing copper and mild steel coupons to palm biodiesel (B100) in the presence and absence of two different corrosion inhibitors at room temperature (25–27°C) for 60 days. Benzotriazole and adenine were added to palm biodiesel at 100, 200, 300 ppm concentrations. In molarity, these concentrations will be 0·72, 1·44, 2·16 mol L−1 and 0·64, 1·27, 1·90 mol L−1 for benzotriazole and adenine respectively. Exposed metal surfaces were characterised by SEM, EDS and atomic force microscopy analysis. Results showed that mild steel surface has degraded comparatively less than that of copper surface in palm biodiesel without corrosion inhibitors. However, benzotriazole was found to be more effective in corrosion inhibition of copper and mild steel than that of adenine in palm biodiesel.

Analysis of tribological properties of palm biodiesel and oxidized biodiesel blends

ABSTRACT Biodiesel has become an increasingly significant alternative fuel to replace conventional diesel completely or partially. Although biodiesel has several advantages, such as environmental friendliness, renewability, and reduced emissions, it also has major drawbacks. Tribology is one of the major concerns for biodiesel usage, in which biodiesel lubricity deteriorates by usage and/or by storage because of its oxidative nature. The present study aims to investigate the lubrication behavior of oxidized and pure palm biodiesel blends by using a four-ball tribotester machine. Tests were carried out in diesel, pure biodiesel (B100), their blends (B10 [10% biodiesel in diesel], B20, B30, and B50), and oxidized biodiesel (Oxd B100) and its blends (Oxd B10, Oxd B20, Oxd B30, and Oxd B50). Tests were conducted at room temperature under a normal load of 40 kg for 1 h at 1,200 rpm. Surface analyses were carried out by scanning electron microscopy, energy-dispersive spectrometry, and optical microscopy, and fuel analysis was performed by gas chromatography–mass spectroscopy. Diesel fuel showed the highest wear and friction. Surface deformation, wear, and friction decreased as the biodiesel concentration increased in the blend. Oxidized biodiesel blends showed improved lubricity compared to pure biodiesel and blends. However, Oxd B100 showed higher wear than Oxd B50.

Evaluation of CrAlN multilayered coatings deposited by PVD magnetron sputtering

The purpose of this experimental work is to evaluate the mechanical and tribological properties of chromium aluminum nitride (CrAlN) coating deposited on hypereutectic Al–Si-alloy. The microstructural, topographical analysis, and composition of CrAlN-coated substrates were examined by using scanning electron microscopy and energy-dispersive spectroscopy, whereas phase formation was analyzed by X-ray Diffractometer (XRD). Atomic force microscopy (AFM) images were taken from the substrate surface before and after the coating. The scratch adhesion of film-to-substrate was measured by using scratch machine. In an effort to understand the critical point, loads were identified by Scratch track in terms of load vs. depth as a function of scan distance. Moreover, the critical load as the beginning of chipping or spallation of the coating was studied. The tribological properties of CrAlN coating were evaluated by pin on disc tribometer at room temperature. XRD analysis showed that CrAlN successfully deposited with a preferential orientation along the (1 1 1), (2 0 0) and (2 2 0) peaks. The AFM images of coated sample confirmed that the surface roughness was lower(Ra = 14 nm) as compared to uncoated sample (Ra = 46 nm). The hardness of coated hypereutectic Al–Si-alloy was increased about 5.8 times as compared to uncoated sample. The coefficient of friction and wear rate of coated specimen were found to be improved. The coating adhesion strength of 2341 mN was obtained with coating parameters for deposition of DC power (350 W), RF power (200 W), temperature (175 °C), and nitrogen flow rate (5%).

A Critical Review on Physical Vapor Deposition Coatings Applied on Different Engine Components

ABSTRACT Friction and wear in different engine components have crucial effects on the engine performance, combustion efficiency, oil consumption and lifetime of the internal combustion (IC) engine. Under certain loads, speeds, and temperatures, the metallic components of the IC engine, especially the piston and valve system suffer from a higher friction. Thin film coating is one of the novel techniques to reduce the frictional forces and improve the mechanical properties of engine components. Due to some versatile tribological properties, increasing attention has been paid to the physical vapor deposition (PVD) technology in the recent decade to deposit thin film coating on engine components. This article presents a comprehensive literature review on thin film coatings for IC engine components deposited by PVD technique. Issues related to tribological properties (wear and coefficient of friction) and mechanical properties (hardness and roughness) are also highlighted. Scientific improvements are presented in the light of literature. It is revealed that PVD coating is significantly effective on wear resistance, scuffling resistance, surface roughness, and friction of the components in IC engine. Laboratory test and data from actual service so far suggest that the plasma-activated electron beam evaporation coating is perhaps one of the best choices for smooth surface finishing with improved mechanical and tribological properties. However, there are still some problems in its practical usage. This compressive review paper presents the major shortcomings of PVD coatings on IC engine components and the possible solutions if any. Finally, a number of issues have been reported which need to be encountered for further studies.

Investigation of the mechanical properties of electrodeposited nickel and magnetron sputtered chromium nitride coatings deposited on mild steel substrate

Abstract Electrodeposition and magnetron sputtering techniques have been employed for the deposition of Ni and bilayer NiCrN coatings, respectively, on mild steel substrate. Ni electrodeposition was performed using sulfate Watt’s bath, while magnetron sputtering was performed on electrodeposited Ni using DC power 350 W and base pressure of 3 × 10−5 Torr in order to prepare bilayer NiCrN coatings. Structural and mechanical properties of Ni and bilayer NiCrN coatings have been investigated using various characterization techniques such as SEM-EDX, XRD, hardness, adhesion testing, etc. SEM analysis reflects the formation of spherical/nodular particles of varying sizes in NiCrN coating whereas Ni coating shows irregular, agglomerated, and non-uniform distribution of particles. Formation of hard CrN phase in NiCrN coating has been confirmed by XRD and EDX. NiCrN coating exhibits better hardness in comparison with Ni coating due to the formation of nitride phase. Micro scratch testing of bilayer NiCrN coating shows better interlayer adhesion and adhesion with mild steel substrate. The combination of electrodeposition and magnetron sputtering can produce inexpensive NiCrN coating containing hard CrN phase with better mechanical properties for automotive applications.

Scratch adhesion characteristics of PVD Cr/CrAlN multilayer coating deposited on aerospace AL7075-T6 alloy

Purpose – The purpose of this study is to design and develop a new functional coating system for aerospace AL7075-T6 alloy that would evaluate the mechanical properties of the coating. Design/methodology/approach – This paper outlines the scratch adhesion characterisation of Cr/CrAlN coating using a combination of radio frequency (RF) and direct current (DC) physical vapour deposition (PVD) magnetron sputtering. The surface morphology, microstructure and chemical composition of the Cr/CrAlN film were evaluated by optical microscopy (OM), field emission scanning electron microscopy (FESEM) integrated with energy-dispersive X-Ray spectroscopy (EDX) and atomic force microscopy (AFM). The film-to-substrate adhesion was measured by a scratch test machine manufactured with a detection system, motorized stages, penetration depth sensors, optical microscope and tangential frictional load sensors. Findings – The AFM and ultra-micro hardness results showed an increase in surface roughness to about 20 per cent and h...

Laser Composite Surfacing of Ni-WC Coating on AA5083 for Enhancing Tribomechanical Properties

ABSTRACT Laser composite surfacing (LCS) has emerged as an alternative photon-driven manufacturing technology for the fabrication of composite coatings to enhance the tribomechanical properties of various aluminum alloys. The current research presents an analysis on optimization of laser processing parameters for Ni-WC composite coating deposited on AA5083 aluminum alloy in order to improve its tribomechanical properties. To carry out the investigation, Taguchis optimization method using a standard L16 (34) orthogonal array was employed. Thereafter, the results were analyzed using signal-to-noise (S/N) ratio response analysis and Pareto analysis of variance (ANOVA). Finally, confirmation tests with the best parameter combinations obtained in the optimization process were made to demonstrate the progress made. Results showed that the surface hardness (953 Hv) and roughness (0.81 μm) of coated AA5083 samples was enhanced by 9.27 and 13.14%, respectively. The tribological behavior of LCS samples was investigated using a ball-on-plate tribometer against a counterbody of 440c steel. It was revealed that the wear of the Ni-WC-coated samples improved by around 2.5 times. For lower applied loads, the coating exhibited an abrasive wear mode and a reduction in plastic deformation.

Structural and mechanical properties of (Cr, Ni) N single and gradient layer coatings deposited on mild steel by magnetron sputtering

Ternary single and gradient layer (Cr, Ni) N thin films were deposited on the mild steel substrate by unbalanced magnetron sputtering technique in order to evaluate mechanical properties for machine tools and automotive applications. Microstructure, chemical composition, surface morphology and phase analysis were carried out using field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy and X-ray diffraction, respectively. Both single and gradient layer of (Cr, Ni) N coatings show a significant increment in mechanical properties such as hardness, adhesion strength and surface roughness along with the reduction of friction coefficient. Mechanical tests revealed that the hardness of the gradient layer increased up to 3.1 times due to the formation of Cr2N and Ni phase whereas single layer showed the least friction. Single layer CrNiN layer exhibited 27.2% less surface roughness (Ra) in comparison with gradient layer. High values of surface roughness, hardness, thickness and friction could be correlated with high film-to-substrate adhesion (Lc2) for the gradient layer.