Mechanical Properties, Thermal Stability and Microstructures of W-Re-ZrC Alloys Fabricated by Spark Plasma Sintering

Abstract

Tungsten materials, used as friction stir welding tools, undergo severe plastic deformation and even collapse at high operating temperatures. In order to improve the low-temperature toughness and high-temperature strength, W-10wt.%Re-0.5wt.%ZrC alloys were processed by high-energy ball milling and subsequent spark plasma sintering. Single solid-solution W-Re powders with typical body-centered cubic structures were achieved when the milling time increases to 50 h. The microhardness, tensile properties, thermal stability and microstructures of this sintered W-10wt.%Re-0.5wt.%ZrC alloys were investigated. Synergetic effects of the solute Re and nanosized dispersion particles induce improvements in low-temperature toughness and high-temperature strength. The alloy suffers ductile fracture at 300 °C, which is about 400 °C and 300 °C lower than that of the spark plasma sintered pure W and W-0.5wt.%ZrC, respectively. Besides, this W-10wt.%Re-0.5wt.%ZrC has a high ultimate tensile strength of 818 MPa and uniform elongation of ~ 8.1% at 300 °C. Moreover, the microstructures and hardness remain stable even after 1500 °C anneal. Based on a detailed microstructure analysis, the mechanisms for the enhanced strength, low-temperature ductility and high thermal stability are proposed and discussed. Grain boundary mobility is impeded by the kinetics constraint through dispersed particles pinning and solute Re atoms dragging, which leads to improved thermal stability. The formation of Zr-C-O particles is most probably attributed to ZrC particles capturing and interacting with impurity oxygen during sintering.

Selective Electron Beam Melting (SEBM) of Pure Tungsten: Metallurgical Defects, Microstructure, Texture and Mechanical Properties

“…That high thermal stress could cause tearing along grain boundaries, which are embrittled by the oxidation and resulting impurities [ 4 , 9 , 22 , 23 ]. It has been reported that a high concentration of oxygen and impurities segregate to the grain boundaries during the cooling process of melted tungsten in SLM [ 9 , 24 ], and the strength of pure tungsten and tungsten alloys are greatly affected by the oxides distributed at grain boundaries [ 22 , 25 , 26 , 27 , 28 ].…”

Preparation, Mechanical Properties and Strengthening Mechanism of W-Re Alloys: A Review

“…The results showed that the average coefficient of friction (COF) and wear rate of the W-25Re significantly decreased after adding the HfC, effectively improving the tribological performance of the W-25Re [ 95 ]. Though the HfC improved the high-temperature strength of the W-25Re, it also reduced the toughness of the W-25Re, ultimately leading to intergranular fracturing and wear failure [ 96 ].…”

“…It was found that the recrystallization temperature of the W-1Re-0.5ZrC was about 1600–1700 °C, which was significantly higher than that of pure W (1200 °C) [ 37 ]. Miao et al observed that the microstructure and hardness of W-10Re-0.5ZrC changed little after annealing at 1500 °C for 1 h. The tensile strength and elongation behavior of W-10Re-0.5ZrC at 300 °C were 818 MPa and 8.1%, respectively [ 96 ]. Recently, Miao et al studied the effects of ZrC on the properties of W-25Re-0.3ZrC.…”

Selective Electron Beam Melting (SEBM) of Pure Tungsten: Metallurgical Defects, Microstructure, Texture and Mechanical Properties

“…That high thermal stress could cause tearing along grain boundaries, which are embrittled by the oxidation and resulting impurities 4,9,18,19 . It has been reported that a high concentration of oxygen and impurities segregate to the grain boundaries during the cooling process of melted tungsten in SLM 9,20 , and the strength of pure tungsten and tungsten alloys are greatly affected by the oxides distributed at grain boundaries 18,[21][22][23][24] .…”