Masami Ishii

A study of cast alloys with partially dispersed graphite: I: The process of partial dispersion with uncoated carbon microballoons

Abstract A study of cast alloys with partially dispersed graphite was carried out to improve the mechanical properties as well as to retain excellent wear resistance. Uncoated carbon microballoons (carbospheres) instead of graphite were only dispersed by a centrifugal casting machine to surfaces requiring wear resistance or lubrication. With pure aluminium, aluminium alloys and tin-based Babbitt metal, carbonized layers extended to a height of 30 mm from the bottom of the specimens and they had a maximum thickness of 1.2 mm. Partial dispersion is due to the poor affinity between the carbon and the molten metal. The casting alloys developed have a smooth surface and no shrinkage from solidification. Factors affecting the mechanism of partial dispersion and remaining problems are discussed: some successful examples are presented.

A study of cast alloys with partially dispersed graphite II: The process of partial dispersion with uncoated flake graphites

Abstract The mechanism of partial dispersion of uncoated flake graphite particles was investigated and compared with that of carbon microballoons (carbospheres) investigated earlier. Two types of flake graphite particles and the same base metals as previously used were investigated. The dispersive power of uncoated flake graphites was relatively small compared with that of spherical carbon balloons. For dispersion a temperature of 50 – 100 °C above the melting point with G = 1500 (where G is a non-dimensional gravity variable) is required with pure aluminium and its alloys. The variation in surface roughness of cast aluminium alloys containing flake graphites is due mainly to the magnitude of the centrifugal forces; the roughness decreases with increase in the acceleration (expressed in terms of G ). The dispersive width of the graphitic layers and the clearance ratio are related; the width increases with ratio up to D / d = 2.5.