Development of Ag-Cu-Zn-Sn brazing filler metals with a 10 weight-% reduction of silver and same liquidus temperature

With BrazeTec BlueBraze the manufacturers in HVACR industry have an alternative filler metal with 10 weight-% less silver but same brazing temperatures. The performance of these new alloys has been evaluated in several tests. The evaluation included wetting investigations, metallographic examinations, joint strength at different temperatures and pulsation and corrosion resistance. The results of these tests will be presented in this paper.

New filler metal systems for the brazing of titanium alloys

It＇ s well known welding takes the leading role in development of titanium structures. However, in number of cases technological processes of brazing are more appropriate and, sometimes, being the single possible, in particular, during production of multilayer thin-wall structures. It should be noted that brazing filler metals of Ti-Cu-Ni, Ti-Zr-Cu-Ni, Zr-Ti-Ni and Cu-Zr-Ti systems in a form of plastic foils, as well as in powder form are mainly used in world practice for brazing of titanium alloys. Present work provides the results of complex investigations of brazing filler metals of Ti-Zr-Fe, Ti-Zr-Mn and Ti-Zr-Co systems using differential thermal analysis, light and scanning microscopy, X-ray microspectrum analysis. Data on melting ranges of pilot alloys were obtained, and liquidas su^Caces of given systems using simplex-lattice method were build. Brazing filler metals covering brazing temperature range of current structural titanium materials based on solid solutions as well as intermetallics were proposed. Structure, chemical inhomogeniety and strength characteristics of brazed joints were studied. It is determined that brazing of solid solution based alloys （OT4, VT6 ） using indicated brazing fiUer metals ensures strength characteristics of joints, which are not inferior to that obtained with application of known brazing filler metals even if they are received at lower brazing temperature.

Brazed joints of CBN grains and AISI 1045 steel with AgCuTi-TiC mixed powder as filler materials

The brazing process of cubic boron nitride （CBN） grains and AISI 1045 steel with AgCuTi-TiC mixed powder as a filler material was carried out.The joining strength and the interfacial microstructure were investigated.The experimental results indicate that the spreading of the molten filler material on AISI 1045 steel is decreased with the increase of TiC content.A good interface is formed between the TiC particulates and AgCuTi alloy through the wetting behavior.In the case of AgCuTi＋16wt% TiC,the strength of the brazed steel-to-steel joints reached the highest value of 95MPa dependent upon the reinforcement effect of TiC particles within the filler layer.Brazing resultants of TiB2,TiB,and TiN are produced at the interface of the CBN grains and the AgCuTi-TiC filler layer by virtue of the interdiffusion of B,N,and Ti atoms.

Numerical simulation of filler metal droplets spreading in laser brazing

A finite element model was constructed using a commercial software Fidap to analyze the Cu-base filler metal droplet spreading process in laser brazing, in which the temperature distribution, droplet geometry, and fluid flow velocity were calculated. Marangoni and buoyancy convection and gravity force were considered, and the effects of laser power and spot size on the spreading process were evaluated. Special attention was focused on the free surface of the droplet, which determines the profile of the brazing spot. The simulated results indicate that surface tension is the dominant flow driving force and laser spot size determines the droplet spreading domain.

An effective strategy towards construction of CVD SiC fiber-reinforced superalloy matrix composite

In this work,a modified approach for preparing CVD SiC fiber-reinforced superalloy matrix composites was rationally developed.The composites were fabricated by vacuum hot pressing(VHP)process using precursor wires coated with(Al+Al2O3)diffusion barrier layers and GH4169 superalloy coatings.BNi-7 brazing filler metals were introduced on the surface of precursor wires in order to decrease the temperature of the VHP process.It was found that the VHP temperature was reduced by about 100℃,and the melting,diffusion,nucleation and growth processes of BNi-7 fillers at 900?C motivated the recrystallization and plastic flow of the matrix under the increasing pressure,thereby a compact composite composed of intact SiC fibers and fine equiaxial grain structure superalloy matrix was achieved.Meanwhile,the elements were distributed homogeneously among the fibers in the composite and no interfacial reactions occurred.This method provides a new insight for designing and manufacturing high-quality composites in practical engineering.