51����, the largest American-owned heat treater in the United States, is proud to support NASA’s Artemis II mission. Our expertise spans thermal processing of raw materials, nickel-based tubing, and critical aerospace components—playing a vital role in bringing next-generation space technology to life. At the core of some of these components is the 6Al–4V titanium Launch Abort System (LAS), one of the most complex safety systems ever engineered. The LAS aboard the Orion spacecraft functions as a rocket capable of outrunning another rocket in an emergency. In the event of a catastrophic launch anomaly, its manifold enables the abort motor to ignite and safely propel the crew module away from the rocket. Designed to endure extreme conditions with zero margin for error, the LAS represents the pinnacle of aerospace safety and performance. 51���� is honored to contribute to this mission-critical technology, providing the precision, reliability, and advanced thermal processing that space exploration demands.

The success of Artemis II is set to energize this month’s Space Symposium in Colorado Springs. Visit us at Booth 705 to discover how 51����’ advanced thermal processing solutions are helping shape the future of space exploration.

Space Symposium Information

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Our Greenville, SC facility has once again been awarded Nadcap 24-Month Merit Status for heat treating, brazing, and carburizing—an elite recognition reserved for companies that consistently demonstrate superior quality and process excellence.

We’re incredibly proud that PRI has acknowledged our team’s unwavering dedication to meeting strict specifications, executing every process with precision, and upholding a culture of quality day in and day out.

This achievement reinforces 51����’ ongoing corporate commitment to delivering world-class thermal processing solutions you can trust.

Congratulations to our entire Greenville team!

Nadcap Heat Treating Services

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The 7th Annual 51���� Sales & Marketing Summit took place this year near our Souderton, PA facility, bringing together sales managers from all six 51���� commercial heat-treating locations. The team collaborated on sales forecasts, shared updates on new processes and plant developments, and aligned on key strategies for the year ahead. Following the meeting, the group enjoyed a team-building outing at Topgolf.

No matter the region—North, South, East, or West—our mission remains the same: deliver exceptional customer service and provide meaningful value to every customer we serve. With over 200 years of combined experience in thermal processing and metalworking, our sales team is equipped to support your most demanding heat treating needs.

Reach out to any of our sales managers to discuss your next project.

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Greenville, SC, October 28 – 51���� is proud to announce the installation and commissioning of a new 10-bar vacuum furnace at its Greenville, South Carolina facility.

Manufactured by sister company Solar Manufacturing, this state-of-the-art horizontal vacuum furnace features a working zone measuring 48” wide x 48” high x 96” deep and can process loads up to 12,000 pounds. The system’s advanced vacuum pumping package achieves an ultimate vacuum level of 1×10⁻⁶ Torr, ensuring superior performance for processing titanium and other high-grade alloys requiring pristine vacuum environments.

Steve Prout, President of 51���� Southeast, commented: “We’re proud to offer our customers another regional option for high-pressure quenching of large components and workloads, while also providing the opportunity to reduce processing costs through economies of scale. This addition reinforces our ongoing commitment to innovation, quality, and customer value.”

For more information about the Solar Atmospheres Greenville facility, contact Mike Paponetti at (864) 970-0111 ext. 1406, or mikep@solaratm.com.

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1. What are some of the first steps I should take before sending parts out for vacuum heat treating?

Before vacuum thermal processing, ensuring the parts are free of foreign object debris (FOD) is essential. This includes removing contaminants like manufacturing oils, coolants, and machining residue. It’s also important to communicate whether the coolant used was water-based or oil-based—this helps your heat treater select the most effective cleaning method.

Many vacuum heat treaters use solvent degreasers for oil-based coolants and hot water/soap-based rinses for water-based coolants. Providing this information up front helps determine how to best prepare your parts for heat treatment.

Bottom line: Failing to address FOD can result in spotting, discoloration, or worse—surface contamination.

2. You made sure the parts are clean; now, how about the vacuum furnace?

Much like a home oven, vacuum furnaces require periodic cleaning—referred to in our world as a “bake-out.” This process removes residual FOD or contaminants left from previous runs.

Typical bake-out temperatures:

• Austenitic (300-series) steel grids, fixtures, and baskets: ~2150°F
• Furnace-only bake-out: ~2300–2400°F

Reaching these temperatures ensures even entrapped moisture in graphite components is eliminated—crucial for maintaining a clean process environment.

3. Okay, so the parts are clean and the furnace is clean. Are we ready to run?

Almost! One final but critical step: check the furnace leak rate.

• For most steels, aim for 20 microns/hour or less
• For reactive metals (like titanium), 5 microns/hour or less is ideal

Remember, all vacuum furnaces leak to some degree—perfection doesn’t exist in commercial heat treating. But keeping leak rates low is key to producing bright, shiny, contamination-free parts.

4. Now for the easy part: the thermal cycle. Right?

Well… not quite!

If you’re using partial pressure gas or backfill gas (nitrogen, argon or helium), you must also monitor the dew point and oxygen content of the process gas. When treating alloys that oxidize easily—even small traces of water vapor or oxygen can cause surface issues.

While dew point measures moisture, it does not measure oxygen. Using oxygen sensors alongside dew point monitoring provides a more complete picture of gas purity, ensuring optimal conditions for clean, bright results.

Also, consider the vacuum level:

• For 300/400 series stainless steels or PH alloys, a vacuum in the 10⁻⁴ Torr range (graphite hot zone) is typically sufficient.
• For titanium or reactive alloys, you’ll need a 10⁻⁶ Torr vacuum, which usually requires an all-metal (molybdenum) hot zone.

While graphite furnaces are capable, all-molybdenum systems offer superior part cleanliness for highly reactive materials.

Lastly, ensure proper thermocoupling of the load. Use contact thermocouples directly in a part or in a heat sink that represents the maximum cross-section. Poor thermocoupling can lead to a false sense of temperature stability—you may think the load is cool, but when the door opens, parts could still be hot enough to oxidize instantly (turning blue).

5. I followed all your recommendations, and the parts are still discolored! Why?

Even with every precaution, discoloration can still occur—and it’s understandably frustrating. But it’s important to distinguish between:

• Discoloration, which is superficial and doesn’t impact performance
• Surface contamination, which is detrimental, as it alters the surface microstructure

To confirm the difference, consider sending a representative part to a metallography lab. These labs can characterize the near-surface condition, helping you determine next steps—ranging from simple Scotch-Brite cleaning, to a chemical or mechanical etch that removes a few thousandths of material.

And featured in Today’s Medical Developments Magazine:

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1. What type of furnace do I need?

Atmosphere or air furnaces work well for bar, sheet, or plate materials that will have stock removed afterward. Finished machined components and additive manufactured builds should be done in a vacuum furnace. When choosing a furnace, you must know if the furnace can hold the proper temperature tolerance throughout the run. If parts need to comply with industry and aerospace specifications, the furnace must demonstrate it can maintain ±10°F in the furnace work zone envelope.

2. Can I combine varied sizes and thicknesses in the same run?

There’s no need to run two loads if all can be done in one. AMS2759/3, Table 4 will give you an idea of thickness overlaps. A well-spaced load, not densely packed, will always achieve the best results. I’ve personally heard of bars being aged in their received bundles, which predictably causes a wide range of hardness variations. This is a clear sign of over and under-aging conditions, with the inside not getting hot enough and the outside exposed to heat for too long.

3. Everything went well with the aging cycle, but the hardness levels are nonconforming.

We operate at risk when we only complete the age harden of PH alloys. We must assume the upstream solution treatment (typically done at the mill) was performed accurately. This includes making sure the PH grade is cooled to below a specific temperature before the age harden. I assume the furnace was loaded (not densely packed), calibrated, surveyed, and thermocoupled correctly. When diagnosing a problem like this, you must take a piece, solution treat, and age it. If the hardness falls within the specified requirement, improper solution treatment was the root cause.

4. My customer is asking for H900, which develops a 40-47 HRC. However, my customer wants 40-43 maximum HRC.

We’ve seen these types of requests for HRC ranges that have only one or two points. In many cases, you must explain what’s feasible. PH Stainless grades usually have wider hardness ranges because there’s variability in chemistry and/or the response to the age harden. Plus, many specifications don’t allow you to deviate on the initial age harden cycle. H900 requires 900 ±10°F for 1 hour +15 minutes -0 minutes. That’s it. That’s where you must start. From our experience, this cycle typically develops a 44-46 HRC, so now you’re anywhere from 1HRC to 2HRC over the maximum.

If hardness exceeds the maximum specified, you can re-age at the same temperature (recommended) or even go 10°F higher to reduce the hardness by a point or two. But re-aging may cause the hardness to fall below 40HRC, resulting in a re-solution anneal and starting all over again.

5. Will my finished parts distort? Is there any concern about size change or distortion in raw bar stock?

People use PH grades because they believe they don’t move dimensionally. Not true. They distort minimally when compared to other quench and tempered alloys. Major steel mills have literature with predictable size contraction based on the age harden or H COND. Distortion, however, is very unpredictable, especially for parts made from hardened bars. In these situations, AMS2759/11 also discusses stress relieving of PH alloys 100°F below the final age temperature. I’ve seen this minimize distortion and heard of less movement of the parts, especially in elevated temperature applications.

For more information: ��Vacuum Age Hardening

And featured in Aerospace Manufacturing and Design Magazine:

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Greenville, SC, October 28, 2024 – 51���� Greenville, SC facility is pleased to announce it has been awarded Parker Aerospace approval. This achievement expands 51����’ reach, offering five facilities able to assist customers with Parker Aerospace thermal processing requirements.

Steve Prout, President of 51����’ Greenville facility, shared: “We are excited to provide our customers in the Southeastern U.S. with another regional solution for aerospace and defense thermal processing. This approval allows us to save our customers time and money while maintaining the exceptional quality they expect.”

51���� offers a wide range of vacuum thermal processing services, capable of handling development cycles and loads of up to 50,000 pounds at temperatures as high as 2400°F. As an AS9100 and Nadcap-accredited company, 51���� ensures every product meets the highest industry standards, giving customers confidence in the reliability and precision of their heat treatments.

For additional information on our processing options and our capabilities, contact Mike Paponetti at mikep@solaratm.com or call 1-855-934-3284.

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1: When I send my 17-4PH parts out for vacuum age hardening they are returned with discoloration. Isn’t the purpose of vacuum heat treating to eliminate that?

It is not uncommon for 17-4PH and similar alloys (15-5PH, 13-8MO etc.) to exhibit some discoloration even after being processed in a vacuum furnace. 17-4PH is precipitation age hardened at a low temperature, between 900°F-1150°F, where even a relatively low residual of water vapor in the vacuum furnace may produce a slight Chromium oxide during the cycle. This is commonly called “heat tint”. Discoloration may also be caused by inadequate cleaning.

2: I have some 17-4PH parts with heat tint and my customer will not accept them as-is. What do I do?

Consider glass bead blasting if acceptable to your customer. If glass bead blasting is not acceptable, parts could potentially be solution treated and re-aged. The solution heat treatment temperature is 1900°F. When vacuum is used, this temperature is in the range of Chromium oxide reduction. It is recommended to utilize a partial pressure with Argon to prevent the vaporization of the copper that exists in 17-4PH (not a concern at age hardening temperatures). A challenge is 17-4PH must be cooled below 90°F after solution treatment (Ms finish) and this is generally not possible to achieve without removing the parts from the furnace, thereby reintroducing new water vapor between solution and age. There is a risk of size change or distortion from this process, and it should be avoided if possible.

3: What is the best way to reduce the risk of heat tint when vacuum age hardening 17-4PH?

The best way to avoid heat tint is to utilize an all-metal hot-zone vacuum furnace that will achieve a very low vacuum level, around 5×10^-6 Torr. In this case, the residual water vapor level will be so low heat tint should not be observed.

4: I currently only have access to a graphite-insulated vacuum furnace, what can I do to avoid heat tint during age hardening?

If the vacuum furnace hot-zone is graphite-insulated (the most common type of vacuum furnace), parts may be shielded with stainless steel or titanium foil. This is generally effective however it increases the total processing time (and cost) since parts are shielded from the energy in the furnace. Foil is not inexpensive and further increases cost. Foil is also a safety hazard; the edges are sharp and one wrong move can cause deep cuts to skin.

5: Is gas purity, dewpoint, and leak rate of the vacuum furnace a consideration in avoiding heat tint?

Yes! Process gas should have no more than about 10PPM of residual oxygen and a dewpoint below about -80°F. If the gas isn’t clean and dry, everything else will have been in vain. This is usually monitored at the point furthest from the supply to detect any leaks in the overall system. The vacuum furnace should also have a very low leak rate, normally about 10 microns per hour or less. At that rate, assuming the rise is linear (which it will not be, it slows down as the Delta P decreases) it would take nearly 9 years for the furnace to leak up to atmospheric pressure.

For more information: ��Vacuum Age Hardening

And featured in Today’s Medical Developments:

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Greenville, SC, April 8, 2024 – 51���� Greenville, SC facility is pleased to announce it has been awarded Lockheed Martin Space Systems approval. With this approval, now all five 51���� facilities are an option for our customers with Lockheed Martin requirements for thermal processing services.

Steve Prout, President of 51����’ Greenville facility states: “We are proud to once again provide our customers in the Southeastern U.S. with another regional option for aerospace and defense thermal processes, saving them time and money while continuing to deliver the high level of quality required.”

With the ability to support vacuum thermal processing needs ranging from development cycles to 50,000 pound loads at temperatures of up to 2400°F, 51���� provides AS9100 and Nadcap quality accredited heat treatments, providing our customers with the confidence their product is being processed as specified.

For additional information on our processing options and capabilities, contact Mike Paponetti at mikep@solaratm.com or call 1-855-934-3284.

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1. Why would I want to use vacuum oil quench (VOQ) instead of a high-pressure gas quench (HPGQ)?

Good question. We all understand a high-pressure gas quench is often better for dimensional stability and guaranteed bright and shiny parts. Unfortunately, HPGQ is no match for the cooling rate of conventional liquid quenchants (water, oil, polymer, salt) when it comes to certain alloys and large cross-sectional thicknesses. Sometimes the part is just too big to effectively cool with a gas, no matter the pressure.

Another limiting factor to be considered when choosing a quench medium is the customer specification itself. For example, AMS2759 / 1 does not allow HPGQ of 4130, 4140 or 4340 steel. These alloy steel grades are frequently used to make various aircraft parts. The requirements are very clear, only oil/polymer shall be used. When you add other requirements for things like surface finish, surface contamination and distortion control, VOQ is the only option.

2. Does VOQ minimize distortion vs. traditional quench and temper processes?

Yes. Keep in mind that a VOQ furnace, really all vacuum furnaces, are loaded at room temperature to avoid any initial thermal shock. Second, vacuum furnace loads are heated uniformly via radiant heating around the part, limiting temperature variation during the ramp. These factors have proven to minimize distortion over traditional practices. Then there’s the transfer mechanism from the vacuum furnace chamber to the oil quench tank itself. With transfer times of less than 30 seconds, you do not have to worry about areas of the furnace load beginning to cool excessively before it hits the oil. Plus, there’s oil quench itself. Oil is the Goldilocks quenchant for steel. Not too fast resulting in excessive distortion or quench cracking but also not too slow for incomplete hardenability.

3. Do I still have to worry about decarburization or oxidation in a VOQ furnace?

The hardening in a VOQ furnace is done after pumping the furnace down to less than 100 microns. We have examined bolts, nuts, landing gear, pistons and everything in between with no measurable layer of decarburization. There’s no discernable surface contamination period. At elevated temperatures, the source of most surface contamination in non-ferrous and ferrous alloys is the air we breathe. By holding a 100 micron or lower vacuum chamber pressure, we can remove the oxygen to eliminate any risk of oxidation or decarburization. Also, without any oxygen, there’s no risk of combustion meaning no flames during the quench. It is a much safer process.

4. What’s the transfer time from the furnace chamber to the oil tank?

The transfer time from the vacuum chamber to the oil quench vestibule is anywhere from 20 to 45 seconds depending on how the transfer mechanism is set. Because the entire process is fully automated, load thermocoupled and video recorded there is no variation from load to load. And because it is so fast, there is no risk of excessive temperature loss before the furnace load hits the oil. Which, as we already discussed, helps ensure quench uniformity and minimize distortion.

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5. I have a Prime specification that calls out different oil temperatures. Can the oil temperature be changed? What about Martempering?

The VOQ can utilize different types of quench oil. Solar uses a medium speed quench oil with a preferred operating temperature of between 120°F and 160°F. With an external oil heater, the oil temperature can be adjusted as needed to meet the required quenchant temperature. So, if you switch out a standard quench oil for a marquench fluid, then you could very easily convert it to a vacuum marquench furnace.

For more information: /vacuum-heat-treating/vacuum-oil-quench/

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