Effects of Silicon Addition on Physical and Mechanical Properties of W, W–Ni, and W–Ni–Co Alloys Fabricated by Powder Metallurgy

Abstract

This present study focuses on the effects of 1, 5, 10, 15, and 20 wt% of silicon (Si) addition on the densification, microstructure, and mechanical properties of tungsten (W), tungsten–nickel (W–Ni), and tungsten–nickel–cobalt (W–Ni–Co) alloys. The alloys are synthesized using high‐energy planetary milling of W, Ni, Co, and Si powders for 10 h, followed by conventional sintering under a hydrogen atmosphere at 1500 °C for 2 h. It has been observed that 10 h planetary milling results in the formation of intermetallic compounds (W5Si3, Ni4W, and NiSi2) in these alloys. The formation of various silicides is observed after sintering, namely, W5Si3 and WSi2 in WSi (1–20) and NiSiW, W5Si3, NiSi, and NiSi2 in W–Ni–Si (1–20) and W–Ni–Co–Si (1–20) alloys through the reaction of Si with W and Ni. The density values of 6.4, 6.3, and 8.5 g cm−3 are achieved for W‐20Si, W‐10Ni‐20Si, and W‐10Ni‐3Co‐20Si alloys, respectively. The hardness values of the alloys increase with the percentage of Si, which is attributed to the formation of brittle and hard silicides. In the case of W‐10Ni‐3Co‐20Si alloy, a maximum hardness of 10.6 GPa is observed. The W‐1Si, W‐10Ni‐1Si, and W‐10Ni‐3Co‐1Si alloys exhibit compressive strength values of 552, 1554, and 1567 MPa and ductility values of 7, 15, and 13%, respectively.