Effect of V, Ti, and Ce on Structure and Performance of NM400

To improve the performance of NM400, V, Ti and Ce were added in NM400. The effect of alloy on grain size, precipitation, hardness and toughness was studied. The result shows that V and Ti can improve the performance by grain refiner and dispersion-strengthening. By further adding Ce, the size of grain and precipitations of V and Ti is significantly reduced, the solid solution quantity of V and Ti and the amount of precipitation are increased, and the precipitation shape transforms from cube to sphere. Therefore the hardness and toughness of steel are greatly improved. In this study, 0.2% V and 0.2% Ti were added into NM400. As a result, the precipitation of V and Ti, in form of carbide and nitride, was the smallest and dispersed, and the grain size was the smallest, which leaded to the best performance. The conclusion is that, to ameliorate the performance of NM400, the optimal additive amount of V and Ti is 0.2% no matter whether adding Ce or not.