The contact fatigue and the wear of DADI class aluminum cast iron

Abstract

In the present work there are given the results of experimental investigations of contact fatigue and the wear of deformable high strength ADI (DADI) class aluminum cast iron depending on the phase ratio in metallic matrix. It is shown that: Modification of cast iron melt with the magnesium vapor gives the opportunity the low silica (0.5-0.7% Si) high strength cast iron to be received, in which the concentration of sulfur will not exceed 0.002%. Besides, the type and degree of austenite transformation of the received cast iron can easily be varied so that required ratio of phase components such as upper bainite, lower bainite, martensite, carbide and the retained austenite could be provided in the metallic matrix and therefore the hardness in the range of 30-57HRC can be given. The wear rolling and rolling with creep tests carried out on the specimens tempered till different levels of hardness showed strong dependence of contact fatigue and the wear on the amount of retained austenite in the samples with optimal ratio, required for keeping the high wear resistance of wearing surfaces, of bainite and martensite phase components in the matrix structure. The stated parameters of the contact fatigue and the wear gives us reason to treat the high strength DADI class aluminum cast iron as an efficient substitute for the expensive steel as a constructional material for manufacturing the critical parts for high pressure multistep gas pumping compressors.

High Temperature Oxidation of Slurry Aluminized Deformable Austempered Ductile Iron (DADI)

“…In contrast, the growth of the Al and Fe oxides is much limited and this allows to observe some of the mass losses at the beginning of the oxidation in the as-received and non-annealed DADI. Although we did not investigate these particular samples after short oxidation times, one can hypothesize that some flake-like graphite was present in the non heat-treated samples compared to the heat treated ones because the selected annealing fosters spheroidization of graphite [4]. In agreement with the findings of Lin et al, the flake-like graphite would induce faster oxidation and decarburization [32].…”

“…For the latter, the samples went through austenization at up to 900 O C in air for 20 minutes and subsequently quenched in water. They were then tempered at 380°C and 270°C for respectively, 2 and 3 hours to relax stresses and to obtain a fine-grained structure [4,5]. Regardless of the annealing treatment, the main feature of DADI's microstructure is the presence of coarse spheroidized graphite shown in Fig.…”

“…The low density Deformable Austempered Ductile Iron (DADI) has been designed to exhibit outstanding mechanical properties including high strength and toughness and good wear resistance, possibility to control its hardness values and easy machinability [1][2][3]. Therefore, DADI has potential applications for different engineering fields like in the automotive sector as a worthy substitution to the more costly steels [4][5]. However, its behaviour at high temperatures has not been studied yet because the formation of unprotective iron oxides is anticipated in relation to its chemical composition (Fe, 3.6 C, 2 Al, 0.8 Si, 0.4 Mn, 0.04 Mg, wt%).…”