It is important that during debinding, all binders are completely removed from components and contaminants that may foul the pumping system or the furnace are evacuated. These contaminants impact quality and fiurnace performance during sintering. The VFS Model VDS (Vacuum Debind/Sinter) design solves this problem by using not one, but two vacuum pumping lines.
Binders are removed by one pumping line and they are carried through the furnace bottom. The pumping line includes an optically dense, water cooled baffle trap with a removable insert for ease of maintenance. The design uses an additional water cooled trap also with removable (replaceable) filter inserts in front of the vacuum booster to collect residual binder material.
In case high vacuum is required, a second vacuum pumping line is connected to the high vacuum diffusion pump's main poppet valve. The high vacuum pump is available for sintering after the binder removal portion of the cycle. The sintering process can also be run with process gas if required.
Sintering is a process needed for a number of different parts and applications including metal injected components and powder metal parts, 3-D metal printing components of various types, and beading applications including abrasives.
The process is as follows:
- The parts are heated to the binding agent's vaporization temperature.
- The temperature is held at this level until all outgassing of the binding agent is complete.
- Debinding segment control is enabled by applying a suitable partial gas pressure that is above the vapor pressure temperature of the other elements in the alloy base material. The partial pressure is normally between 1 and 10 Torr.
- The temperature is then increased to the sintering temperature of the base alloy and maintained to make sure that solid state diffusion of the part occurs. The parts and furnace are then cooled. Based on the application of component metallurgical requirements, cooling rates can be controlled to meet hardness and material density requirements. The chart shows an example of a typical debinding/sintering cycle, which includes the use of a partial pressure gas during the debinding phase, and rapid gas quenching to meet specific material hardness requirements.
Figure 1. VDS Process Description.
Performing sintering and vacuum debinding in a single cycle does not only save the money and time of heat treaters it results in more consistent and superior part quality. The key benefits of the VFS vacuum debinding and sintering furnace system are:
- Quicker processing turnaround - This single-cycle technology enables virtually unlimited design flexibility.
- Higher process quality - Vacuum versus atmospheric
- Reduces contaminants to the furnace and components
- Produces clean and bright components – A requirement of the medical industry
- Furnace reliability and component repeatability - Is maintenance "friendly" for cleaning and contaminant removal
Sintering Part Applications
Several industries rely on sintered parts and components including:
- Medical parts especially implants
- Automotive such as power transmissions, gears & sprockets, camshafts, diesel particulate filter and valve seats
- Tools such as screwdrivers, drills, cutting/grinding tools
Figure 2. Sintering part applications.
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