scholarly journals Microstructure and Properties of Tungsten Heavy Alloy Connections Formed during Sintering with the Participation of the Liquid Phase

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4965
Author(s):  
Paweł Skoczylas ◽  
Zbigniew Gulbinowicz ◽  
Olgierd Goroch

Tungsten heavy alloys (THA) are used in the defense industry for subcaliber bullet cores due to their high density and strength. Typically methods of joining tungsten rod elements include: soldering, friction welding or threaded sleeve splicing. The properties of the joints were tested for three types of material containing 90.8, 96.2 and 98.2 wt.%. tungsten, density from 17.3 to 18.4 g/cm3 and strength range 400–1000 MPa. Combination in the liquid phase at the sintering temperature was carried out in a vacuum furnace at a temperature of 1520 °C in a hydrogen atmosphere, and tests used pairs of both identical and dissimilar materials. After that, some of the bars were subjected to additional heat treatment at 1100 °C for 3 h. The tests of the mechanical properties in the static tensile test and the measurement of impact strength showed that the obtained strength of the joints was comparable to that of the parent material. The microstructure analysis showed that the resulting joint area, while maintaining the appropriate roughness of the joined end faces of the bars, is homogeneous without areas of the solidified matrix of the joint line. Research showed that it is possible to bond under sintering conditions with the participation of a solid liquid phase of homonymous and dissimilar THA materials. The strength of joints in dissimilar materials was comparable to a tungsten heavy alloy material with lower strength in the bonded pair while homonymous materials were comparable to the original material. The test results provided a good basis for further research in which the obtained pairs of joints will be subjected to plastic working processes.

2003 ◽  
Vol 344 (1-2) ◽  
pp. 158-167 ◽  
Author(s):  
Yunxin Wu ◽  
Randall M German ◽  
Brian Marx ◽  
Ravi Bollina ◽  
Matt Bell

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2338 ◽  
Author(s):  
Lenka Kunčická ◽  
Radim Kocich ◽  
Zuzana Klečková

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.


2016 ◽  
Vol 16 (4) ◽  
pp. 131-136 ◽  
Author(s):  
P. Skoczylas ◽  
M. Kaczorowski

Abstract The results of structure and mechanical properties investigations of tungsten heavy alloy (THA) after cyclic sintering are presented. The material for study was prepared using liquid phase sintering of mixed and compacted powders in hydrogen atmosphere. The specimens in shape of rods were subjected to different number of sintering cycles according to the heating schemes given in the main part of the paper From the specimens the samples for mechanical testing and structure investigations were prepared. It follows from the results of the mechanical studies, that increasing of sintering cycles lead to decrease of tensile strength and elongation of THA with either small or no influence on yield strength. In opposite to that, the microstructure observations showed that the size of tungsten grain increases with number of sintering cycles. Moreover, scanning electron microscope (SEM) observations revealed distinctly more trans-granular cleavage mode of fracture in specimens subjected to large number of sintering cycles compared with that after one or two cycles only.


Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7365
Author(s):  
Paweł Skoczylas ◽  
Mieczysław Kaczorowski

The results of structure and mechanical property investigations of tungsten heavy alloy (THA) with small additions of rhenium powder are presented. The material for the study was prepared using liquid phase sintering (LPS) of mixed and compacted powders in a hydrogen atmosphere. From the specimens, the samples for mechanical testing and structure investigations were prepared. It follows from the results of the microstructure observations and mechanical studies, that the addition of rhenium led to tungsten grain size decreasing and influencing the mechanical properties of W-Ni-Fe-Co base heavy alloy.


Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7300
Author(s):  
Paweł Skoczylas ◽  
Olgierd Goroch ◽  
Zbigniew Gulbinowicz ◽  
Andrzej Penkul

The paper presents the results of studies on the effects of heat treatment and cold-work parameters on the mechanical properties and microstructure of the tungsten heavy alloy (WHA) with the composition W91-6Ni-3Co. Tungsten heavy alloy (WHA) is used in conditions where strength, high density, and weight are required. The material for testing as rod-shaped samples was produced by the method of powder metallurgy and sintering with the participation of the liquid phase and then subjected to heat treatment and cold swaging. The study compares the effect of degree deformation on the strength, hardness, microhardness, and microstructure of WHA rods. The conducted tests showed that heat treatment and cold-work allowed to gradually increase the strength parameters, i.e., tensile strength , yield strength , elongation ε, hardness, and microhardness. These processes made it possible to increase the tensile strength by over 800 MPa (from the initial 600 MPa after sintering to the final value of over 1470 MPa after heat treatment with cold swaging deformation with reduction of 30%) and the hardness from 32 to 46 HRC.


2013 ◽  
Vol 49 (3) ◽  
pp. 1130-1137 ◽  
Author(s):  
Jose A. Alvarado-Contreras ◽  
Eugene A. Olevsky ◽  
Andrey L. Maximenko ◽  
Randall M. German

Author(s):  
J.B. Posthill

Tungsten-based heavy alloys have received considerable attention since 1935 when McLennan and Smithells reported the development of a 90wt%W-balance Ni,Cu alloy that was produced by liquid-phase sintering. In the past fifteen years the majority of heavy alloy research has concentrated on the W-Ni-Fe system because of its superior mechanical properties. The commercially-produced 90W-5Ni-5Fe alloy basically consists of two phases; a network of contiguous bcc W-phase spheroids (98.8at%W-0.1at%Ni-1.1at%Fe) that are 20-30 μm in diameter embedded in a fcc matrix γ-phase (19.2wt%W-41.4wt%Ni-39.4wt%Fe). The mechanical properties of the alloy are governed by the properties and microstructure of the respective phases and the W-γ and W-W boundaries. This contribution is concerned with a precipitation reaction that occurs within the W-phase.


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