Characterisation of automotive bore material and coatings using atomic force microscopy [Abstract

Homer Rahnejat (1247550)

Jamal Umer (1252764)

Michael Leighton (1259697)

Nick Morris (1256529)

Ramin Rahmani (1250418)

S.J. Howell-Smith (7201925)

English

Loughborough University Institutional Repository

TriboUK 2018 University of Sheffield, 12th-13th April 2018   Characterisation of automotive bore material and coatings using Atomic Force Microscopy  J.Umer1* N.Morris1 M.Leighton1 R.Rahmani1 S.Howell-Smith2 H.Rahnejat1  1Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, UK  2Capricorn Automotive Ltd, Basingstoke, UK *Corresponding author: J.Umer@lboro.ac.uk  1. Introduction  Choosing in-cylinder surfaces is complex. A well-chosen surface has low friction and wear. Conversely, oversight often leads to premature failure. Identification of appropriate surfaces is typically conducted in an empirical manner or through mimicry of tried and tested exemplars found in current engineering practice. This paper demonstrates the use of Atomic Force Microscopy in Lateral Force Mode to characterise typical cylinder bore/liner materials and coatings. The approach integrates LFM with continuum contact mechanics. The real contact area and effective elastic modulus of the surface, including the effect of any reactive surface film are evaluated.  Surface energy and shear strength, as well as the coefficient of friction at the nanoscale are also determined. These properties are measured for 6 cylinder bore materials, including for composite Nickel-Silicon Carbide and DLC, used for high performance engines. 2. Methodology/Results/Discussion Lateral Force Microscopy is used to measure and benchmark the frictional performance of six specimen materials, which are most commonly used as the primary working cylinder bore/liner surfaces for a wide range of internal combustion engines. The friction force is measured with lateral force microscopy over a number of scan areas (1x1 μm2). The boundary shear strength (𝜏) of material is determined by modelling the frictional force data with DMT [1] theory; i.e. using equation (1).  𝐹𝑓 = 𝜏𝐴 = 𝜏𝜋 [3𝑅(𝐹𝑁−𝐹𝑎𝑑)4𝐸∗]2 3⁄   (1) where, 𝑅  is tip radius, 𝐹𝑁  is normal load, 𝐹𝑎𝑑  is measured adhesive force and 𝐸∗ is measured reduced elastic modulus of the surface through indentation with AFM. More information on this procedure is reported by Umer et al [2]. The Scanning electron microscope image for one of the sample; i.e. Nickel-Silicon Carbide coated sample is shown in the figure 1.      Figure 1: Scanning electron microscopy image of Nickel-Silicon Carbide at area of 55 μm x 30 μm The results show the dependence of nano-scale frictional performance of each material with predicted contact area. The elastic modulus and surface energy of the individual surfaces are used to explain the variations in frictional performance.  The electroplated Nickel-Silicon Carbide surface, which is used extensively in race engine applications, is shown to exhibit lowest friction primarily as a result of its relatively low interfacial shear strength. Acknowledgement The financial support of the Engineering and Physical Sciences Research Council (EPSRC) and BP Castrol under Doctoral Centre for Embedded Intelligence and University of Engineering and Technology Lahore under the faculty development programme are acknowledged.  References  [1] B.V. Derjaguin, V.M. Muller, Y.P. ToporovEffect of contact deformations on the adhesion of particles. J Colloid Interface Sci, 53 (2) (1975), pp. 314-326 [2] J. Umer et al., “Asperity level tribological investigation of automotive bore material and coatings,” Tribol. Int., vol. 117, pp. 131–140, Jan. 2018.  

Characterisation of automotive bore material and coatings using atomic force microscopy [Abstract]

https://repository.lboro.ac.uk/articles/Characterisation_of_automotive_bore_material_and_coatings_using_atomic_force_microscopy_Abstract_/9558980/files/17190926.pdf

Characterisation of automotive bore material and coatings using atomic force microscopy [Abstract]

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