Interfacial segregation of Ti in the brazing of diamond grits onto a steel substrate using a Cu-Sn-Ti brazing alloy

Abstract

Diamond grits were brazed onto a steel substrate using a prealloyed Cu-10Sn-15Ti (wt pct) brazing alloy at 925 ЊC and 1050 ЊC. Due to the relatively high concentration of Ti in the brazing alloy, the braze matrix exhibited a composite structure, composed of ␤ -(Cu,Sn), a Cu-based solid solution, and various intermetallic compounds with different morphologies. The reaction of Ti with diamond yielded a continuous TiC layer on the surfaces of the diamond grits. On top of the TiC growth front, an intermetallic compound, composed of Sn and Ti, nucleated and grew into a randomly interwoven fine lacey structure. An interfacial structure developed as the interwoven fine lacey phase was semicoherently bonded to the TiC layer, with the Cu-based braze matrix filling its interstices. The thickness of such a composite layer was increased linearly with the square root of isothermal holding time at 925 ЊC, complying with the law of a diffusion-controlled process. However, at 1050 ЊC, the segregation behavior of Ti and Sn to the interfaces between the TiC layer and the braze matrix diminished, due to the increased solubility of Ti in the Cu-based liquid phase. The enhanced dissolution of Ti in the Cu-based liquid phase at 1050 ЊC also caused the precipitation of rod-like CuTi with an average diameter of about 0.2 m during cooling. SnTi 3 was the predominant intermetallic compound and existed in three different forms in the braze matrix. It existed as interconnected grains of large size which either floated to the surface of the braze matrix or grew into faceted grains. It also exhibited a nail-like structure with a mean diameter of about 1 m for the rod section and a lamellar structure arising from a eutectic reaction during cooling.

Formation of TiC via interface reaction between diamond grits and Sn-Ti alloys at relatively low temperatures

“…The knowledge on the growth behaviors of TiC is essential for the understanding of failure mechanism of brazed diamond grits, and hence the optimization of brazing process. However, existing research focus more on the characterization of the interface products formed between diamond grits and commercial Ti-containing filler alloys at a certain brazing temperature [9][10][11][12][13], or the technology development of brazing process [14,15]. To the best knowledge of authors, there is little information available regarding the growth behavior of interfacial TiC at variable brazing temperatures, especially at relatively low brazing temperatures [16].…”

Interfacial Bonding Strength Between Brazing Alloys and CVD Diamond

“…Accordingly, Cu-based alloys, such as Cu-10Sn-15Ti, have been presented as ideal brazing alloys for diamond, in which Ti is an active metal and Sn is a melting temperature depressor. A brazing temperature lower than 950°C can be applied to this alloy, and, due to the lack of catalyst for the degradation of diamond and the development of an interfacial TiCx layer during brazing operation, the degradation of diamond can be retarded and the bonding strength can be enhanced (Ref [14][15][16]. For example, the bonding strength between Cu-20Sn-10Ti and diamond was about 344 MPa, evaluated by a tensile test using a Houndsfield tensometer (Ref 2).…”

The Interfacial Reaction between Diamond Grit and Ni-Based Brazing Filler Metal

“…Various alloy systems, such as Ni-BCr alloys, Cu-Sn-Ti, and Cu-Ag-Ti alloys, are commonly used for the brazing of diamond grits. 8) To ensure the development of better quality tools, this aspect of the interfacial reaction needs further research, particularly for the Ni-based filler metal. It's well known that Ni-based filler metal is great in corrosion resistance and bonding strength.…”