scholarly journals System Development for Diffusion Bonding of Multiple Unit Tubes to Produce Long Tubular Tungsten Heavy Alloys

2020 ◽  
Vol 10 (8) ◽  
pp. 2988 ◽  
Author(s):  
Zu Seong Park ◽  
Young Yun Woo ◽  
Sang Wook Han ◽  
Il Yeong Oh ◽  
Tae Woo Hwang ◽  
...  
Keyword(s):  
Diffusion Bonding ◽  
Structural Integrity ◽  
Powder Processing ◽  
Liquid Phase Sintering ◽  
Green Compact ◽  
Furnace Chamber ◽  
Bond Quality ◽  
Bonding System ◽  
Heavy Alloys ◽  
Tungsten Heavy Alloys

A diffusion bonding system to fabricate long tubular parts by joining of two- or more-unit tubes made of tungsten heavy alloys (THAs) is proposed and characterized in this study. The difficulty of powder processing of THA originates from the weak strength of the green compact and the high weight of the THA powders. The long tubular green compact is difficult to handle due to its weak structural integrity. Furthermore, gravity-induced slumping during liquid phase sintering induces dimensional distortion and degrades the mechanical performances. As a clue for solving these problems, the unit tubes are fabricated. However, the mass of green compacts for unit tubes is not sufficiently great as to cause problematic slumping; tubular unit tubes can be obtained without significant difficulty. Fabricated unit tubes are stacked in a furnace chamber and diffusion-bonded to produce a long tubular part having bond strength substantially equal to that of a monolithic tube. The proposed diffusion bonding system was well characterized and successfully applied to the industrial production line. The feasibility was also confirmed by investigating the bond quality, which can be assessed by metallographic microstructure and mechanical property.

scholarly journals Effect of Yttrium Oxide Dispersion on the Microstructure and Properties of Tungsten Heavy Alloys

2018 ◽  
Vol 68 (4) ◽  
pp. 406
Author(s):  
Prabhu Gnanasambandam ◽  
Arockia Kumar ◽  
Tapash Kumar Nandy
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Tensile Properties ◽  
Yttrium Oxide ◽  
Liquid Phase Sintering ◽  
Oxide Dispersion ◽  
Heavy Alloys ◽  
Tungsten Heavy Alloys ◽  
Ods Alloy

<p>Tungsten heavy alloys are considered as two phase composites with 88 to 97 wt% tungsten interspersed in a matrix of relatively low melting elements such as nickel, iron and cobalt. The mechanical properties of these alloys are greatly influenced by the microstructural features such as tungsten grain size, tungsten-tungsten contiguity and matrix volume fraction. Oxide dispersion strengthening (ODS), refinement of tungsten grain size, cyclic heat treatment, addition of alloying elements like Cr, Mo, and Co are some of the methods investigated to improve the microstructural features and thereby the mechanical properties of tungsten heavy alloys. Among these methods ODS has been considered as a promising processing technique since the tungsten grain size observed in ODS alloys is finer compared to the conventional alloys and more importantly the dynamic fracture mode changes from adiabatic shear band to brittle fracture. The present study is mainly focused on investigating the effect of 0.3 wt% yttrium oxide (Y2O3) dispersion on the microstructure and consequently the tensile properties of 90W-6Ni-2Fe-2Co alloy. With 0.3 wt%Y2O3, the ODS alloy (89.7W-6Ni-2Fe-2Co-0.3Y2O3) is processed by two-stage sintering with subsequent thermo-mechanical treatment which includes vacuum heat treatment and swaging. ODS alloy and the conventional alloy (without oxides) are compared based on the microstructures and tensile properties obtained after liquid phase sintering and after final processing.</p>

Liquid-Phase Sintering of Tungsten Heavy Alloys

2010 ◽  
Vol 303-304 ◽  
pp. 55-62 ◽  
Author(s):  
S.F. Moustafa ◽  
S.H. Kaitbay ◽  
G.M. Abdo
Keyword(s):  
Liquid Phase ◽  
Sem Analysis ◽  
Liquid Phase Sintering ◽  
Mechanically Alloyed ◽  
Nickel Iron ◽  
Full Characterization ◽  
Heavy Alloys ◽  
Tungsten Heavy Alloys ◽  
Vacuum Atmosphere ◽  
Sintered Materials

Elemental powders of tungsten, nickel, iron and cobalt of compositions corresponding to (W-3.2Ni-0.8%Fe), (W-3.5Ni-1.5%Fe), and (W-4.5Ni-1.0Fe-1.5%Co) were mechanically alloyed in a tumbler rod mill for 2 hrs. Mechanically alloyed powders were liquid phase sintered at 1500oC for 90 min in vacuum. The sintered materials were heated up to 1150-1200oC in vacuum atmosphere, followed by quenching in water to suppress the impurity segregated at grain boundary. The sintered materials were subjected to cold-working by swaging from 8-30% reduction in area. The swaged specimens were age-hardened at 700oC. Full characterization for both the elemental powders and the sintered tungsten alloys were performed using optical microscopy, SEM analysis, EDS quantitative analysis, X-ray diffraction, hardness and compression testing. This paper will discuss the effects of the elemental powders characterization and the liquid phase sintering parameters on the microstructure and strength of these three tungsten heavy alloys.

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