MECHANICAL DAMPING CHARACTERISTICS OF DUCTILE AND GREY IRONS MICRO-ALLOYED WITH COMBINATIONS OF Mo, Ni, Cu AND Cr
Keywords:damping, alloying, ductile and gray cast iron, graphite, temperature, frequency
Damping behaviour of micro alloyed ductile and gray cast irons were investigated in this study. This was aimed at establishing the effect of composition and microstructural parameters on the damping properties of the micro alloyed cast irons, which have shown promise for utilization in automobile and machine building where enhanced damping performance are vital. Gray cast iron containing manganese as base metal was micro alloyed randomly with molybdenum, nickel, chromium and copper at an amount not more than 0.2 % each; magnesium was added to the melt prior to casting. The microstructures show that both ductile and gray irons were developed, ductile irons consisted of pearlite and ferrite phases with their nodular graphite surrounded by the ferrite phase. The micro-alloyed ductile irons generally had higher storage (78906.39 – 120868.51 MPa) and loss modulus (78906.39 - 120868.51MPa) than the micro-alloyed gray cast irons and the ductile iron composition without alloying elements. Although the damping capacity of the composition without micro alloying elements was highest for all the cast irons (~ 0.085), but it failed at approximately 110 ᵒC, while most of the micro-alloyed ductile irons exhibited satisfactory capacity for vibration energy dissipation up to 190 ᵒC than the micro-alloyed gray irons.