Questions and Answers Archive
by Joseph
What is the HVOF process?
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…
by Joseph
How long should a vacuum furnace hot zone last?
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…
by Joseph
What are the advantages of the Dayton Process compared to other fluoride ion cleaning processes?
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…
by Joseph
Is running a hydrogen partial pressure in my vacuum furnace unsafe?
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…
by Joseph
Can brazing be performed in a vacuum furnace with graphite felt insulation?
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…
by Joseph
How do I choose a gas quench pressure rating for my vacuum furnace?
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…
by Joseph
I outsource my heat treating. How do I decide if I should bring it in-house?
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…
by Joseph
Is brazing the same as welding?
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…
by Joseph
Can a vacuum furnace be used for both hardening and tempering?
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…