There are many. The Dayton Process BV is the only FIC process that uses Teflon as a source of the fluoride ion. This is much safer to handle than the gaseous hydrogen fluoride used in other systems. Gaseous systems must usually be installed in enclosed rooms to minimize the risk of an HF leak and require more preventive maintenance. Unlike gaseous processes, the Dayton Process BV doesn’t require pulsing of gas to create effective cleaning so it is much simpler to operate and cycle times are shorter. Furthermore, the Dayton Process BV involves very dry chemical reactions so there is little risk of intergranular attack. Gaseous processes involve reactions that create moisture thereby increasing the risk of intergranular attack.

For more information please visit our Fluoride Ion Cleaning page

Hot zone life depends on several factors including type of construction, type of use (ie. heat treating versus brazing), cleanliness of the load being processed and maintenance. In general heat treating applications, a properly maintained hot zone should last 5 to 7 years. Once worn out, it can sometimes be rebuilt rather than replaced. VAC AERO can re-build and replace hot zones for any brand of vacuum furnace. We also offer preventive maintenance programs to extend the life of your furnace.

For more information please read our aticle about Hot-Zone Preventive Maintenance

HVOF stands for high velocity oxygen fuelled and is a type of thermal spray process used to apply very dense coatings in a wide variety of materials. Coatings applied by HVOF usually have better mechanical properties than those applied by air plasma spray. The HVOF process is now widely used to apply WC-Co coatings as an environmentally friendly alternative to chromium plating on high strength steel aircraft structural components.

For more information on our Coating Services please click here.

No. Welding involves the melting of the base metal and may take place with or without a filler metal. Brazing involves the melting and re-solidification of a filler metal to form a joint between two base metal components. There is some diffusion of the filler metal into the base metal during brazing but no melting of the base metal itself. Welded joints are usually considered to be mechanically stronger than brazed joints.

There are a lot of factors to consider in this decision and every situation will be unique. A vacuum furnace is a large capital investment and there are other costs associated with setting up in-house that must be taken into account (see our Articles page). You also gain improved turn-around-time and important intangibles such as increased control over a very critical process. Because we offer both heat treating services and equipment, VAC AERO can assist you in conducting an analysis to determine the best-value business solution for your organization.

To find out more about vacuum heat treating in-house please click here.

Hydrogen partial pressures are recommended when processing some alloys (like copper) and vacuum brazing with some filler metals (ie. silver or copper). A hydrogen partial pressure also improves the cleaning action during a vacuum furnace bake-out cycle. When properly design and constructed, a hydrogen partial pressure system is perfectly safe. The VAC AERO hydrogen partial pressure system is designed to meet NFPA standards that limit the concentration of hydrogen in the furnace to prevent explosive reactions with any residual air. Three levels of safeguards are employed. The system is designed so that a hydrogen partial pressure cannot be introduced unless the furnace has first been evacuated to a pressure less than 1 micron (to remove almost all of the air) and reached a temperature higher than 1400°F (above the temperature range where hydrogen and air will react explosively). In addition, the system will automatically revert from hydrogen partial pressure to an inert gas partial pressure if chamber pressure rises above 15 torr. This limits the maximum possible concentration of hydrogen in air to less than 2%, half of the lower explosive limit.
VAC AERO offers both all-metal and graphite-based insulation packages in our vacuum furnace hot zones. Some furnace manufacturers and heat treaters will tell you that vacuum brazing can only be performed in furnaces with all-metal hot zones. VAC AERO has proven this to be entirely false. For more than 10 years, our own heat treating facilities have been brazing difficult-to-join materials like superalloys in properly maintained vacuum furnaces equipped with graphite insulation and heating elements. In fact, we’ve found that graphite insulation offers many benefits over metal insulation for certain brazing applications.
The cooling performance required by a vacuum furnace is dictated by the type of alloy to be hardened. Most air hardening tool steels such as the A and D series can be hardened by gas quenching at pressures of 2 bar or less. Furnaces with gas quench pressure ratings of 6 bar and higher can often be used for hardening some alloys that historically required oil quenching (ie. SAE 4340). VAC AERO has conducted comprehensive research into high pressure gas quenching. We learned that, all things being equal, a significant improvement in cooling performance is achieved when the gas quench pressure is increased from 2 bar to 6 bar. Increasing gas quench pressure above 6 bar (to 10 bar, 12 bar or higher) provides further improvements in cooling performance but to a much lesser extent. The higher the pressure rating, the more expensive the furnace is to build and operate. So, a cost/value decision should also be considered.

Yes, it can, but there are some issues to consider. A standard vacuum furnace heats its load most effectively at temperatures above 1200°F (650°C), the start of the “red heat” range when radiant heating becomes most efficient. Below 1200°F (650°C), temperature uniformity within the furnace becomes a concern. Tempering operations for many alloys take place at temperatures well below the red heat range. Depending on load factors such as mass, configuration and section thickness portions of the load may not get properly tempered. Vacuum furnaces can be built with a convection heating capability to improve uniformity at lower temperatures, but this still may not be sufficient to meet some of the more stringent temperature uniformity requirements.

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