Vacuum Debinding and Sintering for Ultimate Component Purity
Sintering is a process required for many different parts and applications, including powder metallurgy, metal injection molding (MIM) and 3D printing components of various types or beading applications including abrasives. In the Ipsen vacuum process, parts are first 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 provided through the application of a suitable partial gas pressure (usually using argon, hydrogen or nitrogen) 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 up to the sintering temperature of the base alloy and maintained to ensure that solid state diffusion of the part occurs. The furnace and parts are then cooled. Depending upon the application of component metallurgical requirements, cooling rates can be controlled to meet hardness and material density requirements. The chart shown above is 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.
Two Versatile Vacuum Sintering Furnace Models
During the debinding process, all binders must be completely removed from components, and contaminants that could foul the furnace or hot zone must be evacuated. These contaminants will affect furnace performance and quality during the sintering process. Ipsen has two models of vacuum sintering furnaces to solve this problem: the VFS model VDS (Vacuum Debind/Sinter) for completely custom furnace designs and the TITAN® DS debinding and sintering furnace, part of the very popular TIAN modular furnaces.
Both the VFS VDS and TITAN DS vacuum debinding and sintering furnace systems perform vacuum debinding and sintering in one process cycle. This not only saves heat treaters time and money, but also results in superior and more consistent part quality.
The VFS VDS model utilizes two vacuum pumping lines. One vacuum pumping line removes binders and carries them out through the bottom of the furnace. The pumping line incorporates an optically dense, water cooled baffle trap with a removable insert for ease of maintenance. The design utilizes an additional water cooled trap also with removable (replaceable) filter inserts in front of the vacuum booster to collect residual binder material. If high vacuum is required, a second vacuum pumping line is connected to the high vacuum diffusion pump's main poppet valve. After the binder removal portion of the cycle, the high vacuum pump is available for the sintering process. The sintering process can also be run with process gas if required.
The TITAN DS design employs a state-of-the-art binder trap system to efficiently handle and filter charged process gas, critical to avoiding unwanted binder material buildup in pipes, valves and pumps. It features a four- stage effluent trapping system. The first stage knocks down heavy particles and condenses volatile solids and liquids on large surface areas. Stages two and three contains wire mesh screen elements strategically located to filter the binder gradually. The last stage is designed to trap any vapor molecules that might have passed the previous stages. The modular system is designed with heaters to dissolves trapped binder which is then collected in a collection bucket that can be easily removed and changed for cleaning.
Vacuum debinding and sintering in one process cycle not only saves heat treaters time and money, but also results in superior and more consistent part quality. The main benefits of the VFS and TITAN DS vacuum debinding and sintering furnace system are:
- Quicker processing turnaround. This one-cycle technology permits virtually unlimited design flexibility.
- Higher process quality - fewer sintering defects (vacuum versus atmospheric).
- Minimization of contaminants to the furnace and components.
- Production of clean and bright components - a requirement of the medical industry.
- Furnace reliability and component repeatability. Maintenance "friendly" for cleaning and contaminant removal.
Sintering Part Applications
Several industries rely on sintered parts and components including:
- Medical, particularly implant parts
- Automotive - power transmissions, gears & sprockets, camshafts, diesel particulate filter and valve seats
- Tools - screwdrivers, drills and cutting/grinding tools