Understanding the effect of NiB/Co ratio on densification, distortion and compressive deformation of 90W-xNiB-2Fe-(8 – x)Co heavy alloys

Abstract

The present study investigates the densification, microstructure, mechanical behaviour and shape retention capability of 90W-xNiB-2Fe-(8 – x)Co (wt%) heavy alloys with different NiB and Co content. In order to understand the effect of NiB and Co in the sintered heavy alloys, the NiB/Co ratio was varied in between 1 and 5, without altering the weight fraction of W (0.90) and Fe (0.02). Six different W-alloys were processed using powder metallurgy route. In the sintered W-alloys, the presence of intermetallic phases and W-rich channels was observed in the systems with NiB/Co ratio of 1 and 1.5. On the other hand, phase and microstructure analyses of W-alloys with higher NiB content (NiB/Co 2) revealed that intermetallic formation could be averted successfully. Interestingly, W-alloys rich in NiB denied distortion and improved shape retention capability even though NiB formed an early liquid phase during densification of these alloys. Among the investigated alloys, a good combination of hardness of 329.2 ± 14.3 HV3 and compressive strength of ∼1608 MPa was obtained for 90W-6NiB-2Fe-2Co (NiB/Co 3). Overall, this study defines an optimum composition window for utilizing NiB and Co for improved microstructure and mechanical properties with better shape retention capability.