Effects of Eutectic Carbide Content on Erosion Behaviors in Ductile Cast Irons

Abstract

During the casting process of thin-wall parts, due to fast cooling rate or chemical composition of the ductile iron, iron carbide (cementite) may exist in the microstructure that retards the mechanical properties of the iron greatly. In this study we discuss the effects of eutectic carbide contents in relation to the cooling parameters and the erosion behavior of the erosion incident angle on the casting specimens. Different content of eutectic carbide was produced by varying the cooling rate and silicon content. Solid particle erosion tests were performed using a shot-blasting machine with angular Al 2 O 3 particles. The results show that, the largest amount of eutectic carbon (plate-like) exists in the faster cooling rate and lower silicon content. The amount of pearlite and nodules counts produced at lower cooling rates also decreased accordingly. Erosion rate also was found in the same trend that higher carbide content yielded better erosion resistance and lower erosion rates, but the amount of reduction is lower than the amount of increase on the hardness level. The maximum erosion rate occurred at the incident angle equaling to =4:5, and the deepest erosion penetration occurred at an incident angle of =3:6 for four comparison specimens. The impinged surface morphologies of four specimens exhibit cutting and plowed furrows at lower incident angles, but the overlapped chippings at higher incident angles. The erosion mechanisms, at medium and high incident angle erosion, show fatigue crack and subsurface lateral crack propagation in higher eutectic carbide specimen, but platelet peeling-off and internal crack and deformation in lower eutectic carbide specimen. The test also revealed that the failure mechanism of the casting thin plates tend to be ductile-brittle fracture.

Solid-particle erosion behavior of cast alloys used in the mining industry

“…A matrix with a plastic deformation capability gives an alloy a reasonable wear and impact resistance [14,1617]. Although several carbides give cast iron/steel its excellent wear resistance under dry sliding conditions [15], they can cause a detrimental effect during repeated particle impingements [18]. Stevenson and Hutchings [19] studied the wear of hard-facing white cast irons by solid-particle erosion and concluded that harder particles (SiC and SiO 2 grits) as erodent material caused fracture of primary carbides, resulting in material loss and high wear rates.…”