Processing of W and W - Ta alloys via laser powder feed directed energy deposition

Abstract

The microstructure, porosity and Vickers hardness of pure W, W - 15% Ta and W - 21% Ta fabricated by Laser Powder Feed Directed Energy Deposition (LPF-DED) in ambient air and inert build environments were studied in this work. Severe microcracking and porosity were observed in all samples when building in ambient air and Ta was selectively oxidized. Under inert atmospheres, pure W was manufactured with no bulk microcracking and 1.7% porosity. Increased Ta content led to decreased porosity and increased hardness with again no microcracking observed. The lack of cracking in the inert was attributed to the increase in build temperature and reduced oxidation.The decrease in porosity, increase in hardness with W - Ta was attributed to the decrease in liquidus temperature with increasing Ta. Micrographs also show grains refinement with increasing Ta content and a cell structure was reported for W - Ta alloys. This work provides relevent information about manufacturing of high temperature melting materials via LPF-DED.