Author :
Najafi-Zadeh, A.,Golozar-Zadeh, M. A
Abstract :
In the paper presented here, the influence of heat treatment and chemical composition on the microstructure, mechanical properties, oxidation and corrosion resistance of isothermally transformed bainitic, nodular cast iron alloys are investigated.The alloying elements which were added to the base iron included;0-8.5 wt.,Al, 1.8 wt.,Ni, and 0.7 wt.,Cu. The silicon content was kept constant. The base chemical composition (Wt.,) used was; 3.8-4.3,C, 1.5,Si, 0-2-0.08,S, and 0.02-0.04,P. Ductile iron was produced using 75Wt.,Fe-Si and 5Wt.,Mg-Fe-Si.The spheroidising treatment was carried out by plunging technique. Pouring temperature was maintained around 1400 . Each melt was cast in the form of Y-blocks (ASTM-A536-80) in silicate bonded sand mold. All Y-blocks were annealed at 890 for 1 hour. Tensile specimens (ASTM-A536-80) and 10x10x50x mm V-notch impact speccimens were then prepared for austempering processes. Wile the austenitization temperature was kept unchanged (890 ) ,the austempering time and temperature have varied within the range of 15-150 min and 285-375 respectively. All ADI alloys consisted of bainite with various amounts of recained austenite. The matrix microstructure and mechanical properties were strongly affected by the variation of isothermal transformation time and temperature. Conversely, the oxidation and corrosion resistance as well as the mechanical properties were affected by the addition of alloying elements. In this respect, the oxidation and corrosion resistance were mainly affected by alloying element of aluminum. it was also revealed that the presence of alloying ...
