An Application Investigation of W-Fe/C Nanostructured Powders in Fusion Welding

The D707 welding rods were fabricated with the nanostructured and microsized WFe/C composite powders as main starting materials. The scanning electronic microscope, Xrays diffraction and hardness test were used to analyze the microstructures, chemical and phase compositions and hardness. The results showed that the carbides in the microstructures welded with nanostructured powder rods (NPR) were granular and fine, and the most carbides in the microstructures welded with microsized powder rods (MPR) were dendritic, coarse, and severe in compositional segregation. The contents of element W in the carbide welded with NPR and MPR were 71.78% and 64.75%,respectively, which showed that the alloy element transition of the former was better than that of the latter. The microstructure welded with NPR consisted of numerous Fe3W3Ctype carbides, austenite and a small quantity of martensite. And that welded with MPR was composed of numerous Fe3W3Ctype carbides and austenite. The hardness of layers welded with NPR was 61.5HRC aswelded and 65HRC astempered, all of these were higher than that welded with MPR.