Effects of Sintering Conditions on Structures and Properties of Sintered Tungsten Heavy Alloy

Abstract

Probably the most advantageous fabrication technology of tungsten heavy alloys enabling the achievement of required performance combines methods of powder metallurgy and processing by intensive plastic deformation. Since the selected processing conditions applied for each individual processing step affect the final structures and properties of the alloys, their optimization is of the utmost importance. This study deals with thorough investigations of the effects of sintering temperature, sintering time, and subsequent quenching in water on the structures and mechanical properties of a 93W6Ni1Co tungsten heavy alloy. The results showed that sintering at temperatures of or above 1525 °C leads to formation of structures featuring W agglomerates surrounded by the NiCo matrix. The sintering time has non-negligible effects on the microhardness of the sintered samples as it affects the diffusion and structure softening phenomena. Implementation of quenching to the processing technology results in excellent plasticity of the green sintered and quenched pieces of almost 20%, while maintaining the strength of more than 1000 MPa.

Effect of Transition Metals Oxides on the Physical and Mechanical Properties of Sintered Tungsten Heavy Alloys

“…In the final stage, the growth of larger globules occurs at the same time as smaller globules are dissolved. The microstructure of samples sintered at 1500 • C supports the W particle growth through a "solution-reprecipitation" process during sintering, which agrees with previous reports [6,[15][16][17][18][19].…”

“…However, the minor elements cannot be detected by the X-ray diffraction analysis due to the limitations of the X-ray diffraction technique. At the onset of particles bonding, re-arrangement of particles and pore filling happens, and hence rapid densification of the compacts and formation of W-Ni solid solution occurs [19,20]. Due to the presence of nickel in the liquid phase during liquid phase sintering, the effect of nickel on the recrystallization of tungsten has been investigated by several researchers.…”

“…As the sintering temperature increased, solubility and diffusivity of the edges of the tungsten particles in liquid phase are increased and also the coalescence of the small size tungsten globules are also increased, which caused porosity elimination and eventually increases density [22]. Therefore, by increasing density At the onset of particles bonding, re-arrangement of particles and pore filling happens, and hence rapid densification of the compacts and formation of W-Ni solid solution occurs [19,20]. Due to the presence of nickel in the liquid phase during liquid phase sintering, the effect of nickel on the recrystallization of tungsten has been investigated by several researchers.…”

Effect of Rare Earth Metals (Y, La) and Refractory Metals (Mo, Ta, Re) to Improve the Mechanical Properties of W–Ni–Fe Alloy—A Review

“…The higher percentage of tungsten helps to maintain a higher density of the alloy. The powder metallurgy technique is primarily used to fabricate tungsten heavy alloys [ 26 , 27 ]. In a general process, the powders are mixed in a mixer or a ball mill to obtain a homogeneous mixture followed by compaction at a desired pressure in a press to obtain a green compact with sufficient strength.…”

Special Issue: Mechanical Properties in Progressive Mechanically Processed Metallic Materials

“…Several papers published within the Special Issue then deal with processing of metallic powders—assessing and optimizing the processing conditions and evaluating various phenomena of the final products. The paper by J. Málek et al [ 5 ] deals with the effects of the selected processing route on the properties of a biocompatible HfNbTaTiZr high entropy alloy (HEA), for the specific advantageous properties of HEAs have been within the focus of researchers for the last few decades, whereas other researchers focused on a WNiCo tungsten heavy alloy, from evaluating and optimizing the sintering conditions for the initial powders [ 6 ], through numerical simulation of deformation behavior during plastic deformation processing [ 7 ], to thorough investigation of structural phenomena, such as microstrains and residual stress [ 8 ].…”