INFLUENCE OF PROCESS PARAMETER ON PROPERTIES OF CAST IRONS
Keywords:
Flake graphite iron, Spheroidal graphite iron, Gravity cast, Centrifugal cast, Microstructure, Nodules, Wear, Coefficient of frictionAbstract
The properties of cast irons depend on the graphite morphology and characteristics of metallic matrix. Perhaps the most interesting feature of the family of cast irons is the morphology of the graphite phase, and the modifications of that morphology, which occurs as a result of changes in chemical composition, melting and melt handling techniques and the process of solidification and subsequent cooling. In this work an attempt is made to study the effects of process parameters like cooling rate during solidification, centrifugal casting process and gravity casting process of cast irons on morphology and tribological properties. A comparison of microstructure of constituents and tribological properties of specimens is made in gravity cast with natural and rapid cooling, centrifugal and gravity casting techniques. In microstructure for flake graphite iron it has been observed that the gravity casting process with natural cooling produces a flake size range 1 to 2 whereas rapid cooling produces a flake size range 2 to 3. It shows that the natural cooling produces more flakes of type A, approximately by about 50% over that in rapid cooled structure. For spheroidal graphite iron it has been observed that the centrifugal casting produces an increase in the number of bigger nodules and decrease in the number of smaller nodules and an increase of nodules per square mm. It has no effect on nodularity percentage. The result shows that flake graphite iron with normal cooling produces a reduction in coefficient of friction and decrease in wear over that of rapid cooling process. It has been observed that for spheroidal graphite iron the centrifugal effect produces a lower coefficient of friction and decrease in wear compared to gravity cast.
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