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Brazing Metering Plates to Turbine Blades With Nickel

Research Objective
To heat a turbine blade in a vacuum to 2000°F and hold temperature for five minutes for a nickel brazing application.

Parts & Materials Description
Inconel turbine blades, nickel metering plates, nickel braze

Temperature Required
2050°F maximum

Induction Heating Equipment
ABS Mark 2 with high vacuum option and optical pyrometer for temperature measurement; 20kW power supply with a remote heat station containing three (3) 0.75 μfd capacitors (for a cumulative capacitance of 0.25 μfd) and a specially-designed inductor (coil).

Operating Frequency
280 kHz

Heating Procedure
The ABS Mark 2 with a vacuum level of <5x10(-4) torr was used for the testing. A specially-designed inductor was used to provide optimal heating (approximately 80% energy efficiency) to the braze joint area. The temperature of the joint area was measured with an optical pyrometer. RF power from the 20kW power supply was applied to the plate for two minutes. As the plate temperature reached 2000°F, the power was automatically reduced by the pyrometer to maintain the temperature for a five-minute period. A one-minute cool-down Argon quench was used for an overall cycle time of eight minutes.

Conclusion
The metering plates were successfully brazed to the turbine blades with nickel within five minutes at 2000°F. The nickel braze flowed well and the joints were clean. Since only the braze joint area was heated, an additional braze stop-off step was not necessary.

Brazing Metering Plates to Turbine Blades
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