The Role of Niobium in the High Chromium Cast Iron Hardfacing Metal

In this paper,self-shielded flux cored wire including niobium for open arc welding was prepared with 7% niobium element to replace the same number of moles of chromium element in the high chromium cast iron hardfacing metal.The role of niobium in the high chromium cast iron hardfacing metal was studied,the effect of heat input on microstructure and hardness of the high chromium cast iron hardfacing metal was analyzed,by means of color metallography,SEM,EDS,XRD and testing Rockwell hardness techniques.The results showed that niobium element can preferentially combined with carbon to form dispersion distribution of NbC crystal core,to prevent the growth of primary carbides,thus plays a significant role of grain refinement.The heat input in the same hardfacing metal is smaller,whether or not to add niobium element,the size of carbides is finer,the number of cracks is greater,its distribution is more homogeneous and its gap was smaller.The crack distribution can be controlled by adjusting heat input in order to prevernt hardfacing layer falling off.No matter changing heat input or replacing the same number of moles of chromium element with 7% niobium element in hardfacing metal,its Rockwell hardness basically remained constant,both in the 60 HRC or so.