Comparative study on densification, microstructure, hardness, and compressive strength of ZrB2 and NiB-incorporated 90W-6Ni-4Co and 90W-6Ni-2Fe-2Co alloys

Abstract

The present study investigates the densification behaviour, phase, microstructure, shape distortion, mechanical, and thermal properties of ZrB2 and NiB-incorporated 90W-6Ni-2Fe-2Co alloys and compares the findings with 90W-6Ni-4Co alloys. Despite the hindrance of densification by ZrB2, all the sintered alloys achieved a density > 97 % of theoretical. The presence of the ZrO2 phase along with the ZrB2 phase was revealed in XRD patterns of the blended powders. The microstructural analysis confirmed the co-existence of both ZrB2 and ZrO2 phases in ZrB2-incorporated alloys. A reduction in average W grain size from 40.5 mu m to 30.4 mu m was noticed in case of 2 wt% ZrB2 addition. Moreover, ZrB2 assisted in the prevention of shape distortion of the 1500 degrees C sintered samples. The distortion parameter (delta) decreased from 18.22 to 4.12 for 90W-6Ni-2Fe-2Co and 88W-6Ni-2Fe-2Co-2ZrB(2) alloys and from 17.81 to 2.87 for their NiB counterparts. The highest compressive strength of 2022.1 MPa was obtained in 2 wt% ZrB2-added W-Ni-Fe-Co alloy. The maximum bulk hardness of 405.4 +/- 27.8 HV3 was observed in 89W-3Ni-3NiB-2Fe-2Co-1ZrB(2) alloy. The coefficient of thermal expansion (CTE) of the 90W-6Ni-2Fe-2Co-based alloys has also been reported in this research work.