Wear behaviour of carbidic ductile iron with different matrices and carbide distribution

Abstract

Just like other properties, wear resistance is entirely dependent on materials microstructure, which, in turn, is related to the chemical composition and solidification rate that controls phases type, size, amount and dispersion. Depending on the tribosystem, the abrasive wear resistance of ductile iron (DI) may be improved by heat treatment as well as by reinforcing the matrix with hard particles like carbides, typically obtained by alloying with elements such as chromium. The solidification rate mainly depends on wall thickness and mould characteristics. In ductile iron, the solidification rate affects microstructural characteristics, such as nodule size, nodule count, carbide size and distribution and matrix refinement, also including the last to freeze (LTF) amount, size and distribution. This study evaluates the influence of the wall thickness (12.5, 25, 50 and 75 mm) on the abrasion resistance and impact toughness of DI with different matrices reinforced with carbides. Carbidic structures were obtained by alloying the melt with Cr; and the different types of matrices such us pearlitic, martensitic and ausferritc (CADI) were obtained under as cast conditions or by heat treatment. The results reflect the influence of cooling rate on the microstructural characteristics and its relationship with the mechanical properties, particularly the abrasive wear resistance. It was demonstrated that, under the present experimental conditions, the highest carbide content and matrix hardness, obtained from the 12.5 mm thick part with a martensitic matrix, resulted in the highest abrasion resistance.