Effects of minor Ce doping on the microstructure and mechanical performances of a EH47 grade HSLA steel for ship and ocean engineering

The influence of minor Ce doping on the evolution mechanisms of microstructure and mechanical performances of EH47 grade HSLA steel for marine engineering was investigated by microstructure observation and analysis. In the present work, the chemical composition of steels with different Ce contents was designed, and the TMCP hotrolling process was applied to obtain a portion of bainitic microstructure for the purpose of achieve the performance indicators. The microstructures, precipitates, and inclusions of Ce-free and Ce-containing steels were observed and analyzed by using scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD) detector and transmission electron microscope (TEM) equipped with energy dispersive X-ray spectrometers (EDS). The strength, plasticity, and impact toughness of the experimental steels was measured and evaluated. According to the results, after adding rare earth Ce, the microstructures including grains, M-A constituents, and inclusions of steel were refined and optimized significantly. Then, the influencing mechanisms of Ce doping on precipitates and inclusions formation were further discussed in detail. Simultaneously, a clear variation tendency of mechanical properties was presented by Ce addition. The strength and hardness enhanced significantly, and the total elongation declined slightly. Moreover, the impact absorbed energy enhanced from 56 J to 152 J.