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A study on graphite extrusion phenomenon under the sliding wear response of cast iron using microindentation and microscratch techniques. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractThis study focuses on the graphite flakes extrusion mechanism during microindenting and microscratching of cast iron. Observations on the graphite response under abrasive conditions revealed that the matrix deformation which is occurred during a sliding wear condition could have a significant influence on its lubricating performance. Simple microindentation and microscratch tests were conducted to explore the lamellar graphite contribution to tribofilm formation under abrasive wear conditions. The results obtained showed that induced plastic deformation which developed adjacent to the graphite compressed the lamellas and in turn resulting in extrusion of the graphite from its natural position. Further investigations on both indentation and scratch tests indicated that, surprisingly, the graphite began to be fractured and extruded from the centre of graphite lamellas, irrespective of the lamella size. Additionally, a mechanism was proposed to explain the selflubricating and the extrusion behaviour of the lamellar graphite as a result of indentation.

Abstract:The thermal expansion and density of Compacted Graphite Iron (CGI) and Spheroidal Graphite Iron (SGI) were measured in the temperature range of 25-500 °C using push-rod type dilatometer. The coefficient of the thermal expansion (CTE) of cast iron can be expressed by the following equation: CTE = 1.38 × 10

This study focuses on abrasion resistance of Lamellar Graphite Iron (LGI) using microscratch test under constant and progressive load conditions. The interactions between a semi-spherical abrasive particle, cast iron matrix and graphite lamellas were physically simulated using a sphero-conical indenter. The produced scratches were analysed using LOM and SEM to scrutinise the effect of normal load on resulting scratch depth, width, frictional force, friction coefficient and deformation mechanism of matrix during scratching. Results showed a significant matrix deformation, and change both in frictional force and friction coefficient by increase of scratch load. Furthermore, it was shown how abrasive particles might produce deep scratches with severe matrix deformation which could result in graphite lamella's coverage and thereby deteriorate LGI's abrasion resistance.

The purpose of this work was to investigate the relation between shrinkage porosity and the macrostructure. Based on results from an earlier investigation regarding shrinkage porosity and its characteristic features, a test casting was developed. The macrostructure was preserved using direct austempering after solidification heat treatment. Shrinkage porosity was found in regions where it was designed to occur. It was also found that this type of porosity is connected to the atmosphere via defects located on the surface, confirming earlier findings. Beneath the surface, it extends as a three-dimensional network through the casting. The shrinkage porosity was, in some cases, found along the boundaries separating primary crystals, and in some cases, it encircled separate primary crystals. A shrinkage porosity formation mechanism is proposed based on these observations, discussing the importance of a rigid columnar zone, movement of a local thermal centre and how pressure differences developing during solidification influence the formation of shrinkage porosity.