Brazing Services
Aerobraze specializes in the manufacture of high temperature brazing filler metals under the Nicrobraz® and Niferobraz® brands. Aerobraze has a number of high temperature vacuum brazing and hydrogen brazing furnaces designed to produce high quality brazed joints. Before undertaking any brazing process it is necessary to undertake a careful appraisal of the following elements in order to produce satisfactory brazed joints:
- Filler-metal flow
- Base-metal characteristics
- Filler-metal characteristics
- Surface preparation
- Joint design and clearance
- Temperature and time
- Rate and source of heating
- Surface protection/reduction/cleaning by an atmosphere or flux
Brazing Aids
Wall Colmonoys Nicrobraz Stop-Off ® materials and Brazing Aids are designed to protect metal surfaces from the flow of molten brazing filler metal, or to prevent metal surfaces from adhering to each other during furnace brazing. Nicrobraz Stop-Off products are available in two grades: fast drying Type I (lacquer based), and nonflammable Type II (water based). Please see our Brazing Aidsor Nicobraz Stop-off® pages for more details.
Material Preparation prior to Brazing
It is important that the materials to be joined are wet
by the BFM, for this to occur the surfaces must be free from contamination such as dirt, grease and paint films. Some alloys selected for their corrosion or oxidation characteristics have passive surfaces which also influence the ability of the BFM to wet and run. On such materials it is important to maintain a low partial pressure of oxygen within the furnace to promote dissociation of the film and prevent it reforming.
However, there are materials which require additional processing prior to brazing; these alloys are high in titanium and aluminium which form stable adherent oxides. The brazing characteristics of these materials can be improved in a number of way by:
- Nicroblast
- Fluoride Ion Clean
- Hydrogen Clean
The aim of all of these processes is to improve the wetability of the surface by reducing the impact of the oxide forming elements.
By way of an example fluoride cleaning reduces the amount of aluminum and titanium in the surface of a nickel base alloy hence decreasing the tendency for the formation of a stable oxide film.
Typical results from this type of process are shown in the picture opposite :
Aerobraze offers both fluoride cleaning and hydrogen cleaning processes these are tailored to the specific alloy and its brazing requirements; This expertise is used frequently by a range of customers on important development projects.
Aerobraze is able to advise on all areas of vacuum brazing through joint design and surface preparation to correct selection of BFM. It is likely that we have already had experience of working with the type of component / assembly you wish to produce.
