Effects of Chromium on Microstructures and Properties of Carbide Austempered Ductile Iron

By using of microstructure observation,X-ray diffraction analysis,spectrum analysis,Rockwell hardness test,impact toughness and wear resistance experiment,the effects of chromium on microstructure and properties of carbide austempered ductile iron(CAD)I were researched.The results show that after austenite at 920℃ for 1.5 h and austempered at 280℃ for 2 h,the microstructure and the properties of the sample containing 0.5% chromium are the optimal;the as-cast microstructure is composed of 65% pearlite,ferrite and carbide;after heat treatment,the microstructure is composed of remaining austenite,lower bainite and 15% carbide.Its tensile strength is 1420 MPa,hardness HRC is 50.9,impact toughness is 21.37 J·cm-2 and relative wear resistance is increased by 48% than that of samples contain none chromium.