Sintering Behavior of Tungsten Heavy Alloy Products Made by Plasma Spray Forming

Abstract

Refractory metallic thin-walled products of 95W–3.5Ni–1.5Fe (in mass%) were fabricated by plasma spray forming (PSF) in argon atmosphere at 1.01×10⁵ Pa followed by high temperature sintering (1200, 1300, 1400 and 1465°C). Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), Archimedes method, differential scanning calorimetry (DSC) and X-ray diffractometer (XRD) have been employed to study microstructure, solubilities, density, solidus and liquidus temperatures and phases of the parts. Lamellar structure consisting of vertical columnar grains and fine particles was found in PSF deposits. Supersaturated solid solutions were formed in the deposits with the relative density of 88±2%. Solidus and liquidus temperatures of γ phase were measured to be 1392 and 1412±5°C, respectively. Initial lamellar structure was remained in the tested samples after sintering at lower temperatures (1200°C/90 min, 1300°C/90 min and 1400°C/15, 90 min) and turned into granular structure at 1465°C/5, 15, 30, 90 min. In addition, the relative densities of deposits, after sintering at 1200, 1300, 1400 and 1465°C for 90 min, were increased from 88 to 90, 92, 94 and 98±2%, respectively. A five-stage sintering mechanism proposed by us previously has been re-validated and double checked by experimental results.