Effect of holding time on the microstructure and strength of tungsten/steel joints by HIP diffusion bonded using a Cu interlayer

High purity alumina/stainless steel joints were produced via activated molybdenummanganese (Mo-Mn) route using 72Ag-28Cu solder. Microstructures of the metallized ceramic and joint sections were observed by scanning electron microscopy. Joint strength was tested by shear-loading method. Some process factors were characterized and analyzed, which include temperature, holding time and heating and cooling rate in ceramic metallization process. The effects of Ni plating and succedent annealing were also investigated. Experimental results show that, migration of glassy phases is the main mechanism of the ceramic metallization. Glass migration direction is from metallizing layer to ceramic side. In the ranges of temperature and holding time of metallization, joint strength firstly increases and then falls with temperature raising and time extending. More fully sintered metallizing layer can be obtained while the temperature increases from 1200oC to 1500oC, and the time prolongs from 30min to 60min. Over-sintering of the metallizing layer will take place with metallizing temperature of 1600 oC and overlong holding time of 70min, which reduces the joint strength. The slower heating and cooling rate, and the annealing after Ni plating both help enhance the seal strength, due to relieving or eliminating interlayer residual thermal stress. However, too slow heating and cooling rate, such as 5 oC /min, is equivalent to overlong holding time and finally also decline the strength. A thin Ni coating helps solder wet metallizing surface, and stops solder erode metallizing layer.

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Investigation of tungsten/steel brazing using Ta and Cu interlayer

Fusion Engineering and Design ◽

10.1016/j.fusengdes.2016.11.004 ◽

2016 ◽

Vol 113 ◽

pp. 102-108 ◽

Cited By ~ 21

Author(s):

Wensheng Liu ◽

Zixuan Wang ◽

Yunzhu Ma ◽

Qingshan Cai

Keyword(s):

Cu Interlayer ◽

Tungsten Steel

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Cracking of Copper Brazed Steel Joints Due to Precipitation of MnS upon Cooling

Journal of Materials Engineering and Performance ◽

10.1007/s11665-020-05293-9 ◽

2020 ◽

Vol 29 (12) ◽

pp. 8183-8193

Author(s):

Dheeraj Varanasi ◽

Daniel Koncz-Horvath ◽

Anna Sycheva ◽

Peter Baumli ◽

George Kaptay

Keyword(s):

High Vacuum ◽

Holding Time ◽

Critical Conditions ◽

Pure Liquid ◽

Steel Grades ◽

Heat Expansion ◽

Mn Content ◽

Expansion Coefficients ◽

Time Required ◽

Steel Joints

AbstractThe process of brazing of different steel grades by pure liquid copper foil was studied to reveal the critical conditions when cracks do or do not appear in the braze upon cooling without any external load. Steel grades C45 (S 0.030 wt.%, no Mn and no Cr), S103 (Mn 0.25 wt.% and S 0.020 wt.% with no Cr), CK60 (0.75 wt.% Mn, 0.07 wt.% S and 0.15 wt.% Cr) and EN 1.4034 (Cr 12 wt.%, Mn 1.0 wt.% and S 0.035 wt.%) are studied under identical conditions using copper foils of 70-microns-thick. The samples were held above the melting point of copper at 1100 °C under high vacuum for different time durations (between 180 and 3600 s) and then cooled spontaneously. The joints were found cracked during cooling after a certain critical holding time. This critical holding time for cracking was found to decrease with increasing the Mn content and the S content of steel. It is observed that cracking is due to the precipitation of a critical amount of MnS phase upon cooling. The MnS/Cu interface is the weakest interface in the joint (with adhesion ensured only by van-der-Waals bonds), which is broken/separated upon cooling due to difference in heat expansion coefficients of the sulfide and copper phases. Higher is the Mn and S content, shorter is the probable time required for crack to appear in the joint. The braze integrity diagram is constructed as function of solubility product of MnS in steel and holding time showing a stable crack-free technological region and an unstable technological region with high probability of crack formation.

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Influence of Cu-Interlayer Thickness on Microstructures and Mechanical Properties of MIG-Welded Mg-Steel Joints

Journal of Materials Engineering and Performance ◽

10.1007/s11665-016-1945-3 ◽

2016 ◽

Vol 25 (3) ◽

pp. 910-920 ◽

Cited By ~ 21

Author(s):

X. Y. Wang ◽

D. Q. Sun ◽

Y. Sun

Keyword(s):

Mechanical Properties ◽

Interlayer Thickness ◽

Microstructures And Mechanical Properties ◽

Steel Joints ◽

Cu Interlayer

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Rational design of composite interlayer for diffusion bonding of tungsten–steel joints

International Journal of Refractory Metals and Hard Materials ◽

10.1016/j.ijrmhm.2017.10.002 ◽

2018 ◽

Vol 70 ◽

pp. 155-161 ◽

Cited By ~ 18

Author(s):

Qingshan Cai ◽

Wentan Zhu ◽

Yunzhu Ma ◽

Wensheng Liu ◽

Xinkuan Pang ◽

...

Keyword(s):

Diffusion Bonding ◽

Rational Design ◽

Steel Joints ◽

Tungsten Steel

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Interfacial structure and joint strength on Ti(C, N)–Al2O3 cermet/40Cr steel joints with diffusion bonding

International Journal of Modern Physics B ◽

10.1142/s0217979220400512 ◽

2019 ◽

Vol 34 (01n03) ◽

pp. 2040051

Author(s):

Fei Liu ◽

Mingfang Wu ◽

Juan Pu ◽

Fengjiang Wang

Keyword(s):

Solid Solution ◽

Diffusion Bonding ◽

Joint Strength ◽

Pulse Current ◽

Holding Time ◽

Interfacial Structure ◽

Duty Ratio ◽

Continuous Increase ◽

Cu Interlayer ◽

40Cr Steel

The [Formula: see text]–[Formula: see text] cermet to 40Cr steel joint was conducted by liquid phase diffusion bonding under the auxiliary pulse current and using 73Cu–27Ti amorphous foil/Cu foil/72Ag–28Cu foil sandwich foils as the interlayer. The effect of holding time and duty ratio of the pulse current on interfacial structure at the [Formula: see text]–[Formula: see text] cermet side and joint strength were studied. The results showed that the longer bonding time can improve the melting of Cu–Ti foil and the dissolution of Cu interlayer to obtain a higher joint strength. The interfacial structure was composed of the TiCu compounds and Cu solid solution at the cermet side, and [Formula: see text] compounds and Cu solid solution at the Cu interlayer side. The auxiliary pulse current was beneficial to reach a higher joint strength in a shorter holding time. A higher duty ratio would accelerate the dissolution and reaction of cermet to the interlayer, but continuous increase on the duty ratio would result in the over dissolution of cermet into the interface to produce the Ti(C, N) and [Formula: see text] ceramic particles and the decrease on the joint strength.

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