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Vacuum Brazing Furnace

Research on Vacuum Brazing of Alloys

Cemented carbide is widely used in many industries of modern industry due to its high hardness, strength and wear and corrosion resistance, especially in the cutting tool industry, mining industry and oil drilling and other fields. However, because its price is relatively expensive and its machining performance is worse than ordinary steel, it is mostly used in the form of connection with steel matrix materials. Among cemented carbide connection technologies, brazing has become the most commonly used method for heterogeneous cemented carbide connections due to its advantages of relatively low welding temperature, small post-weld deformation, and convenience in welding complex structural parts. Currently commonly used cemented carbide welding tools include various cutting tools, shield bits, coal picks, oil drill bits, dental micro drills and other mature products. However, with the rapid development of modern industry, the operating environment of cemented carbide welding tools has Increasingly extreme, such as its application in deep space exploration missions (lunar exploration projects), extreme service environments have put forward higher requirements for the overall quality of carbide brazing tools.

High-temperature alloy materials are metal materials based on Fe, Ni, Co, and Cr that can work stably for a long time under a certain stress above 600°C. Among them, GH4169 has excellent comprehensive physical properties between -253~600°C. , so GH4169 can be used as a potential matrix material to connect with cemented carbide to meet service requirements under extreme working conditions.

Therefore, research on vacuum brazing of YG6X cemented carbide and GH4169 high temperature alloy was carried out. By studying the influence of brazing materials, brazing processes and base metal surface modification treatments on the microstructure and mechanical properties of YG6X/GH4169 heterogeneous brazed joints, Obtain high-quality dissimilar material brazing joints and combine the excellent properties of the two materials to provide technical support for the forming and manufacturing of carbide brazing tools under extreme working conditions.

The research mainly starts from the following three parts:

1.Brazing material design and performance testing

Starting from the low-temperature performance of the solder, and considering the adaptability of the solder to YG6X and GH4169, an AgCuNiMn quaternary alloy solder was designed, and the thermophysical properties and microstructure of three materials with different Ag, Cu, Ni, and Mn contents were studied. Differences, and a brazing performance test was conducted. By comparing and analyzing the test results, the brazing materials for subsequent tests were selected, and the low-temperature properties of the selected brazing materials and the base metal were tested (test temperature: -238°C) .

The three brazing materials, YG6X and GH4169 were assembled into brazing specimens and vacuum welded. The peak brazing temperature is 860°C, and the holding time is 10 minutes. The average tensile strengths of samples welded by Ag-1, Ag-2 and Ag-3 solders are 214.5 MPa, 413.8 MPa and 432.8 MPa respectively.

2.Vacuum brazing process optimization

This part mainly studies the influence of vacuum brazing process on the microstructure and mechanical properties of YG6X/AgCuNi4Mn8(Ag-3)/GH4169 fiber welded joint, mainly including the influence of brazing temperature and brazing seam gap. By studying and analyzing the intrinsic relationship between the changes in brazing temperature and brazing seam gap, the evolution of the microstructure of the joint, and the changes in mechanical properties, we reveal the microstructure evolution and strengthening mechanism of the brazed joint under different temperatures and different fiber seam gaps, and optimize the process. Parameters improve the mechanical properties of brazed joints.

3.Research on surface modification of base metal to promote solder wetting properties

The fiber material is spread on the surface of GH4169 alloy with different surface conditions. The test temperature is 890°C and the temperature is maintained for 10 minutes. According to the wetting and spreading morphology of the needle material on the surface of GH4169 alloy without Ni coating, it can be found that the needle material shrinks and aggregates on the alloy surface after melting, forming a convex spherical shape. The solder material wets and spreads on the surface of the Ni-coated GH4169 alloy. The solder material is almost flat and integrated into the surface of the sample, showing excellent wetting performance.

The brazing temperature is 890°C and held for 10 minutes. The entire brazing seam structure after welding can be divided into three parts, namely the YG6X/brazing material interface layer, the central area of the brazing seam and the brazing material/GH4169 interface layer. Analysis shows that there is a Ni coating The phase composition of the fiber seam structure in the YG6X/fiber material interface layer and the center area of the brazing seam is the same as that without Ni coating, but there are obvious differences outside the brazing material/GH4169 interface layer. For example, outside point F, the Ni content is extremely high. High Ni-rich phase organization.

Nickel plating modification treatment on the surface of GH4169 alloy can greatly improve the wetting and spreading performance of AgCuNi4Mn8 on its surface and the gap filling performance during the brazing process. The presence of nickel plating mainly affects the microstructure evolution of the interface between the filler metal and the high-temperature alloy in the microstructure of the brazed joint. Compared with the case without coating, there is a certain width of the coating reaction zone at the solder/GH4169 interface in the solder joint with coating. The existence of the coating reaction zone improves the wetting and filling ability of the solder and ensures the tensile strength of the joint. (638.6 MPa) while obtaining high-quality YG6X/GH4169 heterogeneous brazed joints with beautiful appearance.