A small subset of vacuum heat treaters have long found helium for quenching to provide some very substantial benefits, benefits which are best summed up by gas supplier Air Products;

“Vacuum furnace gas quenching using helium can result in higher production rates, improved metallurgical properties, and can reduce overall process costs. Lower heat-transfer properties of argon and nitrogen can require expensive furnace modifications, higher quench pressure and increased blower speeds to achieve the same cooling rates achieved using helium.

Helium’s heat transfer coefficient is 60% greater than that of nitrogen at the same pressure. Also, helium is less dense than nitrogen or argon, which makes it easier to move in the furnace. Furnace fans need less power to circulate helium, therefore, increasing fan speed or pressure becomes a cost-effective practice in accelerating cooling. Additional benefits of helium gas quenching include:

• Like argon, helium is inert and will not react with components being treated. Nitrogen is considered inert in most cases, but can form nitrides in certain materials.
• Parts clean up is minimal compared with oil quenching.
• Helium quenching can open new markets for heat-treating processes that may be limited by conventional gas quenching. For example, heavier loads or parts with thicker cross sections can be quenched at a faster rate.”

The one very definite drawback to helium is the high (and rapidly increasing) price of the gas itself which is why most users of helium utilize helium recovery systems. The reasons for the dramatic price increases include both supply and demand;

“Helium plays a critical role in a number of high-tech applications, from barcode readers to semiconductors to liquid-crystal display (LCD) panels. Magnetic resonance imaging (MRI) machines can’t work without it. Google, Netflix and Amazon have been buying massive quantities of it for their data centers.

Helium is an important but finite resource that must be extracted from the ground. In fact, it’s exclusively a byproduct of natural gas mining.

As a result, supply is getting tight. Helium is notoriously difficult and expensive to store, for the very good reason that it escapes every known container over time. Ever wondered why balloons lose their helium so fast? It’s because the gas’s atomic radius is so small, it can literally diffuse through any solid. Much of it floats up into the upper atmosphere and eventually gets torn away by the solar wind. Helium is the second-most abundant element in the universe, and yet the day is fast approaching when it may no longer exist on Earth.”

All of these factors have combined to triple the price of helium over the past 3 years with more price increases in the works. The end result of these price increases is that many if not all vacuum heat treaters are very aggressively looking at alternatives to helium gas quenching in vacuum furnaces.

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