Effects of alloying elements on hardness improvement and damping capacity of low thermal expansion cast irons

The effects of alloying elements vanadium and molybdenum on hardness and th e linear thermal expansion coefficient of the Invar-type austenitic cast ir ons were investigated. A combined addition of vanadium and molybdenum was f ound to be the most effective for the improvement of hardness without causi ng an increase in the thermal expansion coefficient. Without heat treatment , the hardness value increased up to 180 HB, and the thermal expansion coef ficient was kept at a relatively low value of 4.6 x 10(-6) K-1 with a combi ned addition of 4.6 wt % V and 3.8 wt % Mo. The effects on the damping capa city of graphite morphology, the magnetic domain, and the combined addition of vanadium and molybdenum were also investigated. The good damping capaci ty of Invar-type cast irons was mainly the result of stress absorption in g raphite. As the amounts of vanadium and molybdenum increased, the damping c apacity decreased. This is caused by an increase in the amount of carbides. (C) 1998 Kluwer Academic Publishers.