Copper-based Brazing Filler Metal & Vacuum Brazing of Diamond

---

Diamond has high interfacial energy with general metals and alloys, and cannot be infiltrated by general low melting point alloys, and its weldability is very poor. Studies have found that Al, Fe, and Co can infiltrate diamond in a liquid state, but at a temperature at which they can infiltrate, they have severe erosion of diamond. Strong carbide active elements such as Ti, Cr, W, Mo can infiltrate diamond well, but its melting temperature is as high as 1600 C, and diamond will be severely graphitized at this temperature. Therefore, it is urgent to find alloy materials with lower melting points as solders, and consider adding some active elements to improve the wettability and affinity to diamond, so as to achieve the purpose of not only bonding diamonds but also meeting the good mechanical properties of the matrix. problem. This article uses copper-based alloy solder to discuss how to choose a low melting point solder and discuss the specific brazing effect.

The base material is 45 steel, and the brazing filler metal is Cu-Sn-Ti alloy. Degreasing treatment on the steel substrate and diamond surface before brazing. The brazing test was carried out under vacuum conditions, and the brazing temperature was about 30°C higher than the melting point. After holding for a certain period of time, it was cooled to room temperature with the furnace.

1. Brazing Process

Compressive shear strength test method: Under vacuum conditions, the temperature is increased by 10 C/min during the brazing process, the holding time is 20 min, and then cooled with the furnace. After brazing, use the method shown in Figure 1 to test, and the indenter descending speed is: 1mm/min. The strength test results are shown in Table 1.

Fig 1 Strength test method

Tab 1 The relationship table of the strength of the solder

The strength of the solder alloy increases with the increase of the titanium content. The fracture occurs at the bonding surface of the poly chip and the solder. After partial fracture, a layer of fine diamond is distributed on the surface of the solder, where the diamond is in the poly chip. In other words, the fracture occurs between the diamond powder in the poly wafer and the filler. In the actual production and use process, the strength of the solder may be greater than the current test results.

Cu-Sn-Ti alloy is an ideal bonding agent. The liquid phase alloy wets the diamond completely at high temperature; it has sufficient bonding force for diamond; and Ti can react with C to form TiC, and the brazing filler metal and diamond form metallurgy Combine.

(1) Brazing a single layer of diamond with an alloy solder containing a strong carbide forming element Ti. The solder has good wettability to diamond, and the carbide forming elements segregate on the diamond surface, causing the diamond and the solder to form between the substrate and the substrate. Chemical metallurgical bonding improves the holding power of the matrix to the diamond.

(2) The copper-based brazing filler metal can realize high-strength bonding with the steel substrate after brazing.

(3) The best brazing process for B5 is 880 °C~900 °C, and the process requirements can be reached within 10 min to 15 min.

Learn more:

Vacuum Heat Treatment Furnace

Vacuum Nitriding Furnace

Copyright: SIMUWU Vacuum Furnace