Effect of graphite on folded metal occurrence in honed surfaces of grey and compacted cast irons

Abstract

Grey cast iron (GCI) and compacted graphite iron (CGI) are the most employed materials to manufacture cylinder liners. The use of diamond tools to hone the surfaces resulted in an increase of the so-called folded metal occurrence. This irregularity can reduce the performance of engines and investigations to understand it have been made. In this sense, the current study aims to correlate the variation of graphite and the folded metal occurrence. Different samples of GCI and CGI were extracted directly of engine blocks, resulting in four metallurgical conditions. Topographical analysis was conducted in an optical interferometer and a dedicated routine to count the folded metal was developed using 3D images. Folded metal occurrence can be associated to a specific region of topography and to an increase in the graphite area fraction. Experimental evidences were provided revealing cross-sectional images of grooves using a scanning electron microscope. In addition, the present investigation shows that a larger amount of folded metal was related to the microstructure of thicker walls of compact graphite iron. PAPER Nomenclature CGI Compacted graphite iron C-thin Compacted graphite iron from thin wall C-thick Compacted graphite iron from thick wall GCI Grey cast iron Grooves width Average of grooves width (µm) G-thin Grey cast iron from thin wall G-thick Grey cast iron from thick wall Graphite area Area of a specific graphite (µm 2 ) Graphite area fraction RECEIVED

Effects of honing process parameters on residual stress fields of grey cast iron engine cylinder liners: Experimental and numerical study

“…It was reported that in the direction of scratching, passage of indenter causes cracks to be formed in the center of the graphite within the lamellas means that the graphite being compressed and then extruded from its pocket. In addition, do Vale et al 31 investigated the effect of graphite on folded metal occurrence in honed surface of grey and compacted cast iron. Based on their work, because of the low strength of graphite compared to metallic matrix and due to the pressure imposed by the honing process, graphite is extruded.…”

Brazilian Tribology: origin, status quo and future perspectives

“…In the following years, GrMaTS/UTFPR increased its facilities, acquiring a universal tribometer, an optical interferometer, and other equipment for material characterization. Counting again with the support of the foundry company, a surface feature resulting from the honing of cast irons-folded metal -was well described and deserves to be highlighted [308]. Results of lubricated wear [309] and the combination of plasma and laser technologies to improve the performance of vermicular cast irons [310,311] have been published.…”

Some remarks on comparing microgeometrical profiles and the application of replicas in microgeometrical measurements

“…during the wear study of the cylinder liner, Yang et al had to cut the lining [2]. Often also simple characterisation needs cutting the engine cylinder [3,4]. However, if silicone replica is prepared from those parts of the cylinder surface that are interesting from the point of view of wear (e.g.…”