How Technology is Changing Vacuum Heat Treating Process

How Technology is Changing Vacuum Heat Treating Process

Manufacturing Technology Insights | Wednesday, October 06, 2021

Vacuum thermal processing is essential for automotive and aerospace component manufacturers because of industry demands to achieve better quality.

FREMONT, CA: As there are immense industry demands for the best possible quality, vacuum thermal processing is critical for automotive and aerospace component makers. Vacuum technology is employed in two processes, brazing and surface treatment.

The amount of work performed by vacuum brazing vastly outnumbers any other operation that uses vacuum furnaces. The transportation (automotive and aerospace) industries have pushed the usage of vacuum furnaces for brazing to new heights. The utilization of lightweight, high-strength materials has also boosted brazing's prevalence.

Base-metal selection and characteristics, filler-metal classification and qualities, component design, joint design and clearance, surface preparation, filler-metal flow conditions, temperature and time, and rate and origin of heating are the variables that must be operated to generate mechanically sound braze joints.

Some factors influence the behavior of the brazed joint, affecting the capacity to construct a metallurgically sound braze joint. Other parameters impact the characteristics of the base metal, while others impact the communications between the base metal and the filler metal. The base metal is impacted by carbide precipitation, hydrogen embrittlement, heat-affected-zone properties, oxide stability, and sulfur embrittlement. Vapor pressure, alloying, phosphorous embrittlement, and stress cracking are the various impacts of filler metals. Post-brazing thermal treatments, corrosion resistance, and dissimilar-metal pairings are examples of interaction impact. 

Vacuum furnaces can be horizontal or vertical in design, and they offer several technical benefits, including:

The approach allows for the brazing of complicated, dense assemblies with blind passages that would be difficult to braze and clean utilizing atmospheric flux brazing methods.

Vacuum furnaces running at 10-5 to 10-4 mbar (10-5 to 10-4 Torr) remove virtually every gas that can obstruct brazing alloy flow, prohibit the formation of persistent oxide coatings, and facilitate the wetting and flow of brazing alloy across vacuum-conditioned surfaces.

Components that have been adequately processed are discharged in a clean and sparkling state, preventing the need for extra processing.

Without using flux, a wide range of materials, including aluminum, cast irons, stainless steel, steels, titanium alloys, nickel alloys, and cobalt-based superalloys, are effectively brazed in vacuum furnaces.

For the filler metal, various types of nickel, nickel-based, copper, copper-based, gold-based, palladium-based, aluminum-based, and a few silver-based alloys are employed. Alloys with readily vaporized components for decreasing melting points are largely ignored. Copper and nickel-based brazing alloys are the commonly utilized filler metals in the thermal treatment of steel.

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