Structure and Property Studies on Austempered and As-Cast Ausferritic Gray Cast Irons

Abstract

A high-strength and wear-resistant alloyed gray iron with ausferritic microstructure on solidification directly from molten condition could be made in a Ni and Mo alloyed gray cast iron. The as-cast ausferritic cast iron was compared with two conventionally austempered gray iron with and without Ni and Mo additions. The various phase constitution and volume fractions were analyzed using optical, SEM and XRD analyses. The various aspects of the alloy chemistry and processing conditions have been correlated with the microstructure and mechanical properties obtained. The analysis showed that the Ni-Mo alloyed austempered gray iron and the directly as-cast austempered gray iron had similar phase constitutions. The strength of the direct as-cast alloy with ausferritic microstructure was higher than the others due to its higher austenite content and carbide distribution. The wear rate of the conventionally austempered Ni and Mo containing alloy and direct as-cast ausferritic alloys is 20% of the austempered gray iron without Ni and Mo with friction coefficient less than 0.4.

Microstructure evolution in grey cast iron during directional solidification

“…As shown in Fig. 4(a), in addition to some retained austenite in a light grey contrast, the acicular ferrite and bainite structures combined with the lath-shaped martensite in a dark grey contrast are observed in the γ + G region [8]. We deduced that the high-temperature γ phase was transformed into the acicular ferrite and bainite structures combined with lath martensite during quenching at high temperatures, in accordance with others' observations of grey cast iron [9].…”

Archives of Foundry Engineering

“…After machining, the castings could be subjected to heat treatment (soaking and slow cooling-down) resulting in the matrix structure with higher hardness and strength [2,4]. Proper selection of heat treatment parameters permits, like in the case of ADI cast iron, a controlled, partial transformation of the matrix [5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”

Corrosion of porous Ti35Zr28Nb in Hanks’ solution and 3.5 wt% NaCl

“…The use of Ti alloys is largely based on their good corrosion resistance because they spontaneously form a passive film in biological solutions. However, crevice corrosion can be an issue …”