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Vacuum Furnace Systems, controls and Manufacturing
Vacuum Brazing and Vacuum Heat Treating Services
Thermal Spray Coating services, Plasma and High Velocity Oxy-fuel (HVOF) Spray Coatings and Inorganic Paint and Pack Coatings
Vacuum Furnace Technology column by Dan Herring, Metallography column by George Vander Voort, Vacuum Brazing column by Dan Kay, Vacuum Pump column by Howard Tring and other Educational Resources

VAC AERO News, Education & Training

vacuum-furnace-manufacturersVAC AERO Commissions a Vacuum Furnace at an East Providence, RI-based Aerospace Manufacturer

Burlington, April 14, 2014 - The production-scale, 2-bar VAH3436 horizontal vacuum furnace with work zone dimensions of 24” wide x 24” high x 36” is designed to process aerospace parts under high-vacuum and partial pressures with excellent process control and is rated at a normal operating temperature of 2400°F (1316°C). The hot zone is comprised of curved graphite elements and the heavy duty hearth is constructed with quickly removable rails of pure molybdenum designed to support a uniformly distributed load of 1000 lbs at 2400°F.  The vacuum chamber and door are constructed of carbon steel and feature a double-wall, water-cooled design. The furnace operating system is based on VAC AERO's versatile HC900 interactive hybrid control package with SCADA and complete network integration capabilities and remote monitoring and control. The furnace is expected to run at full capacity next month.

Vacuum Technology with "The Heat Treat Doctor"

heat-treating-furnaceResidual Gas Analyzers

A residual gas analyzer or RGA for short is a compact mass spectrometer, designed for use either in the laboratory or out on the shop floor. These devices are often mounted for in-situ use on a vacuum furnace. RGA’s are typically designed for process control and contamination monitoring in vacuum systems. Applications for residual gas analyzers include distinguishing leaks from outgassing, fingerprinting the process background, detecting helium and determining the effectiveness of gas line purging. A typical RGA gas analysis can reveal how much of a particular species is present either in the vacuum vessel or in the pump manifold. RGAs are used in most cases to monitor the quality of the vacuum and easily detect minute traces of impurities in the low-pressure gas environment. These impurities can be measured down to 10-14 Torr levels, possessing sub-ppm detectability in the absence of background interferences.

Vacuum Brazing with Dan Kay

vacuum furnaceDewpoint Control in Vacuum-Furnace Brazing

On a warm, moist day, our earth’s atmosphere will contain a significant amount of moisture in it.  During the night, when the sun has gone down, this atmosphere will become cooled, and will not be able to hold onto the amount of moisture (water) that it could when it was warm, and so, some of that moisture will condense out onto the grass in the form of “dew”.  Then, during the following day, when the sun heats the air up once again, the dew will evaporate from the ground. It is well known that the warmer the gas, the greater will be the amount of moisture that gas can hold. At any given point in time, all gases will have what is called a “dewpoint”.   The “dewpoint” of any gas is the temperature to which that gas must be cooled to get the first droplet of moisture to condense out of that gas (assumed to be at one standard atmosphere of pressure). The “dewpoint” of any gas is the temperature to which that gas must be cooled to get the first droplet of moisture to condense out of that gas (assumed to be at one standard atmosphere of pressure).

Metallography with George Vander Voort

vacuum-furnaceFracture of a 17th Century Japanese Helmet

There was a crack in the helmet which is not visible in this image (some associated damage can just be seen in the lower left side of the helmet visor). The crack was opened and the fracture began at a streak with mostly intergranular fracture and then propagated by cleavage as shown below. Note the intergranular fracture in the center foreground of the image on the left. The walls show transgranular cleavage that propagated from the intergranular origin. Next to the fracture, we see a region of columnar grains at the surface with a small region of finer, more equiaxed grains below and the very coarse columnar grains below that, as shown on the image on the right. The fracture is along the left edge of the micrograph. Note that there appears to be some mechanical twinning in the grains at the fracture edge. The specimen was color etched with Klemm’s I and the hardness was 124.6 HV (~69 HRB).

Vacuum Pump Practice with Howard Tring

vacuum-furnacesOil Sealed Rotary Vane Vacuum Pumps - Background and Designs Part 2: Direct Drive design

As stated last month, in Part 1, this article talks only about one and two stage “medium vacuum” oil sealed rotary vane vacuum pumps that can produce a catalog ultimate vacuum of about 1 x 10-2 Torr (0.01 Torr or 10 microns) for a one stage model and about 1 x 10-3 Torr (0.001 Torr or 1 micron) for a two stage model. Smaller vacuum pumps such as those used in the heating, ventilating and air conditioning industry (HVAC) are not included as they are often only for intermittent use and do not have the design features built into the laboratory sized continuous running vacuum pumps used in industry and science. Larger rotary vane vacuum pumps, ones that require ball or roller bearings to support the weight of the rotor are not included either.

Industrial Heating Magazine

vacuum furnace technologyEffect of Cryogenic Treatment on Properties of Tool Steels

The effect of cryogenic treatment (CT) on the properties of ledeburitic tool steels was investigated. CT is also used in conventional heat treatment to improve mechanical properties and wear resistance and decrease the amount of retained austenite. The technology of CT was developed in the 1960s and still elicits contrary scientific opinions today. Some studies report that CT improves hardness, wear resistance, bending strength, toughness, fatigue strength, etc., but some scientists do not agree. Also, experts do not agree as to the main factor influencing results when CT is applied – austenitizing temperature, cooling rate, quench temperature, holding time, heating rate or tempering temperature.

International Thermal Spray Association

vacuum furnacesHistory and Development of Modern Thermal Spray Guns - Part 2

Using vortex-stabilized units, as described above, coldspray, warm-spray, and hot-spray, each producing impact-fusion, are possible. It is not the same though. Outside water cooling is necessary with nozzle lengths up to 16 in. long using ½ in. bores. The principle is simple. The first couple of inches after the reactants have been introduced into the bore, may be un-cooled. When the flame within the bore is fully stabilized, a small flow of quench water is introduced. Allowing time for a sufficient amount of evaporation of this water to begin limiting the jet stream temperature within the bore — about 6 inches —, then add the powder. Adjust the quench water flow so that the powder being accelerated never melts. It has more than 8 in., or so, to travel to the exit.

Front- and Bottom-Loading Vacuum Furnaces

vacuum heat treating furnacesVAC AERO offers a wide range of vacuum heat treating and brazing furnaces, from small laboratory models to large vertical furnaces, as well as equipment for CUSTOM applications. VAC AERO offers complete turnkey services, including planning, designing, building and installation of vacuum furnace systems and controls. VAC AERO’s experience, proven through decades of service in commercial heat treating, has provided us with valuable insight into the changing needs and rigorous demands of our furnace customers. As a result, VAC AERO has developed a keen understanding of the design and performance of vacuum furnace systems built to meet the most stringent requirements for reliability. VAC AERO’s vacuum furnace design innovations are thoroughly tested in our own heat treating facilities before being offered to our customers. That means better quality, reliability and efficiency to maximize uptime and productivity. Horizontal vacuum models provide great flexibility for general heat treating and brazing applications and Vertical bottom-loading models are ideal for processing large circular parts such as rings, stators or engine casings and long parts like shafts or rolls.

vav_furnace-2.gifThe standard VAV Series Vertical, Bottom-loading, Vacuum Heat Treating and Brazing Furnace can be customized to suit unique applications such as high pressure gas quenching, high temperature heat treating, ultra-clean processing and more.

The furnace is designed to have fast heating rates to very uniform temperatures at high vacuum levels. Standard units are equipped with a gas quench system capable of cooling the load rapidly from processing temperatures at quench pressures up to two bar.

Advanced microprocessor controls are used exclusively to ensure precise control and repeatability. VAC AERO control systems can be integrated with internal networks and offer extensive data collection capabilities. VAC AERO also manufactures auxiliary equipment for quench gas storage and furnace cooling requirements.

Custom or Standard Furnaces Sizes Available


TEMPERATURE UNIFORMITY: Meets or Exceeds AMS 2750 Requirements.


VAC AERO hot zones have unitized construction for easy removal and maintenance. Lightweight design with low thermal mass and inertia for faster quenching and long life.

  • Work Load Size: Standard sizes up to 84” diameter x 84" high. Larger models are also available.
  • Heating Elements: Customer’s choice of lightweight curved graphite, pure or lanthanated molybdenum strip.
  • Hearth: Constructed with quickly removable hearth rails of pure molybdenum designed to support uniformly distributed loads up to 4000 lbs at 2400°F.

    vert_hot_zone-3.gifRadiation Shields: (Graphite-based Construction):

    The standard graphite-based insulation package consists of three layers of carbon felt with a inner facing of graphite foil bonded carbon composite for added protection and enhanced reflectivity. The heat shield package is supported by a stainless steel assembly that also acts as a manifold to distribute the quenching gas uniformly throughout the workload.

    Radiation Shields (All-Metal Construction):

    For ultra-clean processing applications, VAC AERO also offers an all-metal hot zone construction. The standard all-metal insulation package consists of two layers of pure molybdenum sheet backed by three layers of stainless steel sheet. The heat shield package is supported by a stainless steel assembly that also acts as a manifold to distribute the quenching gas uniformly throughout the workload.


    The chamber and heads are a double-wall water-cooled design, primed and painted the customer's choice of colour. The chamber is equipped with all necessary thermocouple jacks, gauge ports, pumping ports and gas quench entries conveniently located for easy access. The tank assembly is vertically aligned with a bottom opening load head. The bottom head and the load are raised and lowered smoothly by a constant speed, ball screw driven lifting jack. Once lowered, the bottom head rolls out from beneath the furnace by means of a powered drive assembly to allow 360° access to the load. The tank is equipped with a powered rotary clamping system to secure the bottom head during processing. A "ground fault" system is used to detect if the load or fixtures touch the heating elements during loading or unloading and will stop the elevator to prevent damage.


    The vacuum pumpdown is automatic and interlocked. The VAC AERO design uses a holding pump to maintain a low pressure on the diffusion pump foreline at all times. This feature, combined with proper timed sequencing of vacuum valves, virtually eliminates backstreaming of pump oils.

    • Mechanical Pump: Roughing Pump and Booster combination appropriately sized for furnace volume.
    • Diffusion Pump: Varian series complete with charge of Dow Corning fluid.
    • Holding Pump: Rotary vane pump.
    • Main, Roughing and Foreline Valves: Right angle poppet valve with electropneumatic operation.
    • Partial Pressure Capabilities: The furnace can be operated at partial pressures up to 1 torr (1000 microns) of inert gas (argon or nitrogen, whichever is used for quenching). Failsafe hydrogen partial pressure systems are also available.


    VAC AERO’s IG Series Quench Gas Storage Systems are available as an option.

    External recirculating inert gas quenching system distributes quench gas through circumferentially located internal nozzles for rapid, uniform cooling of the work load. The system includes:

    • Quench blower powered by electric motor with soft start.
    • Special high efficiency tube/fin heat exchanger.
    • Complete quench piping.
    • Selectable operating pressure.

    vertical_hardwarealarms.gifPROCESS CONTROLS with SCADA:

    The VAC AERO control system is programmable and logic based. The design philosophy of VAC AERO is to simplify control by using the program capabilities to perform as many functions as possible, thereby reducing operator dependence. VAC AERO has also chosen proven hardware components, suitably hardened for an "industrial shop" environment. The system uses a state-of-the-art Hybrid controller to control the machine functions and furnace temperature. The controller integrates with software running on a personal computer to provide Supervisory Control and Data Acquisition (SCADA). Operator interface is provided though an LCD touch-screen mounted in a control panel. An extensive range of standard displays is available.

    The key benefits of this system are:

    • Compatible with plant wide SCADA and network integration.
    • Process cycle validation.
    • Extensive alarm and event management and reporting.
    • Temperature control using advanced algorithms, auto tuning, and multiple PID loops.
    • Operator sign-on/sign-off security provides up to 255 control levels to limit operator control of individual items of plant and equipment.
    • Enhanced maintenance and troubleshooting management and trending.

    Vacuum Instrumentation: A Vacuum Gauge Controller with 2 station, thermocouple gauge and 1 station Penning (cold cathode) gauge is used to monitor the chamber and the pumping system. This instrument is integrated with the process controller to provide dedicated setpoints that control all critical vacuum-related process functions.

    Overtemperature Safety Controller: Digital manual set 0°F - 3100°F, Type S.

    Power Supply: The heating element power is supplied by an A.C. water cooled power supply containing single phase VRT assemblies. Each VRT has a 0 – 100% trim control for optimum temperature uniformity in the hot zone.


    Furnace water system consists of a compact manifold containing all necessary pressure regulators, valves, pressure switches and flow regulators with supply and drain hoses and fittings. As an option, VAC AERO can provide a Dual Loop Cooling System to supply coolant to the furnace.


    The system is shipped complete, tested and ready for installation. VAC AERO offers installation supervision or complete installation services. After installation, a qualified VAC AERO technician will visit the site to commission the equipment and provide instruction in furnace operation. As part of every furnace contract, VAC AERO also provides pre-delivery training in heat treating processes furnace operation and maintenance.

    pdf_fileicon.gifDowload VAV Series Furnace Specs

    pdf_fileicon.gifDowload VAV series Auxiliary System Product Sheet

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