Effects of Y addition on carbide morphology and impact properties of D2 cold work die steel
Yuxiang Liu, Zhigang Wang, Xiao‐Qiang Hu, Ping Zhu, Yukang Xiong, Aiming Zhao, Kuo Cao
Abstract
In this study, heavy rare-earth Y element was added to D2 cold work die steel to improve its carbide morphology and distribution, thereby increasing its impact resistance. A comprehensive study was conducted on the morphology and distribution of carbides in D2 steel in the as-cast, as-forged, and spheroidized annealing states. After the forging process, the degree of breakage of the network distribution of the as-forged M 7 C 3 eutectic carbide morphology in the Y-containing D2 steel increased. As the Y content increased from 0 to 0.0210 wt%, the secondary dendrite spacing of the as-cast M 7 C 3 eutectic carbides as well as the volume fraction and average size of carbide clusters decreased from 43 μm, 16.7%, and 29 μm–31.96 μm, 14.2%, and 23 μm, respectively. After the spheroidized annealing process, the addition of Y increased the M 7 C 3 eutectic carbide spheroidization degree. Moreover, the number of the M 7 C 3 secondary carbides increased from 50/25 to 71/25 μm 2 , and Y addition increased the number of dimples in the impact fracture and proportion of high-angle grain boundaries from 79.1% to 93.4%. Finally, the longitudinal impact toughness of D2 cold work die steel increased from 103.9 to 163.2 J.