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Powder-based Preforms for High Temperature Joining of Dissimilar Metals

Description
WideGap™ from MRi is a joining technology for brazing dissimilar materials in high temperature ranges of 650° to 2000°C. Using liquid infiltration and liquid phase sintering, WideGap™ brazing uses powder based dense and flexible preforms to produce much wider gap braze joints (joint tolerances>0.010 in.) than conventional brazing. These WideGap™ joints are able to accommodate expansion mismatches. They can also be tailored to grade and match the inherent materials’ interface thermal expansion conditions.


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Features

· Permits wide gaps to be brazed

· Prevents brittle phase formation

· Enables dissimilar materials joining

· Lowers use of expensive braze alloys

· Increases joint strengths & ductilities

· Tailored compositions / engineered powder preforms

· Compatible braze alloys & parent fillers

· Matches coefficient of thermal expansions

· Permits grading of joint materials & properties

 
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How WideGap™ Works

WideGap™ technology involves a proprietary production facility and know how (developed over 10 years) for producing flexible mats with binders. In addition, there is significant technical expertise built into the preforms for the joints’ materials/metallurgical interactions (powders in preforms are scientifically selected and engineered e.g. specially sized, special surface conditions, special densities, sometimes made as a composite). This ability to make mats and slurries that hold together and can be formed to shape while maintaining integrity during vacuum furnace firing is essential to the WideGap™ process.

This unique capability forms the underpinning of our know-how! The binders must hold the product together but vaporize at the right time during furnace firing and pass out of the furnace without causing contamination or buildup.


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Applications

  • Brazing to graphite furnace parts
  • Pipeline joining/dissimilar or clad materials
  • Pipeline cladding & repair
  • Dies / Rolls / Mold repairs
  • Conductors / Busses / Coils
  • Electrical Contacts
  • Graphite:Metal Conductors
  • C:C Composite Shafts and Seals
  • Ceramic: Metal joining - thermal protection & management
    - wear protection
    - chemical attack protection
  • Chemical/metallurgical refineries: reactors and related seals
  • Mixers/Blades
  • Hot Gas Nozzles
  • Aircraft & Aerospace Engine Components

 

WideGap Applications

The capabilities of WideGap were demonstrated in a NASA SBIR where the joining of graphite-based heating crucibles and the bonding of refractory composite (C:C and/or C:SiC) components used in government systems were successfully accomplished.

Other Significant Accomplishments Listed in This NASA SBIR:

Successfully demonstrated the joining of graphite to molybdenum and other refractory metals

Joined C:C to C:C and to refractory metals for possible use in rocket engines or processing furnaces

Developed a range of WideGap braze alloy compositions for service temperatures from 850 to 14500C

Demonstrated that WideGap braze preforms can economically join dissimilar materials for high temperature service

WideGap Joint Examples

Graphite WideGap™ (CuTiMo) joined to Mo

mlt16.jpg (8344 bytes)
WideGap™ (BNi5-Ti- SiC) graphite to TZMoly joint.

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WideGap™ (BNi5-Ti- SiC) C:C to TZMoly joint.

mlt17b.jpg (14552 bytes)
WideGap™ (NiCr-Ti- Mo) graphite to TZMoly joint.

mlt18.jpg (11220 bytes)
WideGap™ (NiCr-Ti- Mo) C:C to TZMoly joint.

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WideGap™ (Cu-Ti-Mo) C:C to TZMoly joint.

mlt20.jpg (9566 bytes)


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WideGap™ Products


Currently Copper and Nickel-based WideGap™ preform mats are available and have fond application for joining molybdenum to graphite for operation to over 850°C (1560°F). MRi continues to develop new WideGap™ preforms that are raising the temperature bar (> 1250°C) and capable of joining many combinations of dissimilar and composite materials, including:

- Graphite / Metals

- C:C and C:SiC

- SiC and Alumina to Metals

MRi’s technical specialists are available to review unique applications where the benefits of WideGap™ technology can be used to improve the performance of current joining procedures. Contact Ron Smith at e-mail: rsmith@materialsresources.com or see Inquiries for additional information.

MRi will also enter into customer sponsored development programs to customize WideGap™ to meet specific applications. Contact Ron Smith at e-mail: rsmith@materialsresources.com


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Getting Started With WideGap™ Joining

A family of WideGap™ mats have been developed and are offered as standard products. However, significant know-how must be used to successfully join with WideGap™ mats. Technical issues such as metallurgical tailoring, substrate compatibility and thermal expansion characteristics must be understood to achieve joining satisfactory results.

To assure proper application is achieved, MRi processes inquiries in the following manner:

First, a 10-30 minute teleconference is held to educate the customer on the product and determine the specifics of the customers application and determine if WideGap™ is a potential joining solution

Second, part drawings and written requirements, tooling, and environments are reviewed by MRi’s technical department.

Third, a written proposal with costs is submitted to the customer for consideration.

If special mats (not in our inventory) are required for unique applications, our team has the development experience and production facilities to fabricate different mats and joining protocols. However, a customized joining development program (which involves selection and optimization of powders and process parameters) requires up-front funding by the customer. NOTE: In certain custom mat programs, the development costs can be negotiated into the customers high volume purchase.

For more information on application specific or custom mat development programs contact:

Ron Smith at MRi e-mail: rsmith@materialsresources.com


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Materials Resources International
811 W. Fifth Street
Lansdale, PA 19446 USA
Tel: (215) 631-7111 Fax: (215) 631-7115

Web: www.MaterialsResources.com
e-mail: rsmith@materialsresources.com