Heat treatment & vacuum technology are being used to enhance the properties of materials. Find out more about their fundamentals and applications in AM.

Metal heat treatment

Heat treating of metal materials is the most common process in metallurgy and the heat treatment background is as old as people’s ability to refine metal from the ore.

The goal of performing heat treatment is to achieve the required chemical and mechanical properties of the material that is treated. Currently, all kinds of parts made of metals undergo heat treatment at some point in manufacturing. The most basic metallurgical process is steel heat treatment. Changing its chemical composition allows obtaining required physical properties – from softness to hardness by controlling the heating rate, cooling rate, and critical temperature of the process.

In this section, you will find out more about specific heat treatment types, and heat treating equipment with special regard to the additive manufacturing process.

Common heat treatment processes

A wide range of processing exists, depending on the desired properties of a specific metal. The most common industrial heat treatment processes include annealing, surface hardening process, precipitation hardening, tempering, carburizing, normalizing and quenching.

Heat treatment in R&D

Heat treatment methods are often used in material science and R&D projects in research for new materials or the development of metal manufacturing processes.

Heat treatment in AM

Distortion is one of the main problems encountered in AM processes. Proper stress relieving heat treatment is, therefore, crucial for obtaining high-quality products with optimal metal properties and correct geometry.

Heat treating equipment

The market offers currently numerous metal heat treatment industry solutions from services to devices. The most commonly used equipment is vacuum furnaces that allow heat treating processes in desired temperature range while avoiding metal oxidation thanks to heating metal under vacuum.

One example of such equipment is inFurner vacuum furnace – a versatile device that allows not only for internal stresses relief but also for an annealing process at a specific temperature or quenching heat treatment, during which elements are going through a rapid cooling process.

What is vacuum technology

Vacuum technology is a branch of engineering that deals with creating and maintaining a low-pressure environment, which is typically below atmospheric pressure. This technology finds numerous applications in industries such as aerospace, semiconductor, material science, and manufacturing. One particular application is the use of vacuum technology in vacuum furnaces, which is a type of furnace designed to perform various heat treatment processes in a controlled atmosphere.

Vacuum furnaces

Vacuum furnaces are commonly used in the manufacturing of high-performance materials such as aerospace alloys, ceramics, and carbon composites. They operate by heating a workpiece in a controlled atmosphere, which can either be a vacuum or an inert gas. The primary advantage of using a vacuum furnace is that it allows for precise control of the heating process, leading to improved material properties, reduced contamination, and lower oxidation rates which is especially important when processing reactive metals.

The vacuum technology used in vacuum furnaces relies on the use of high vacuum pumps that can evacuate air molecules and other gases from the furnace chamber. These pumps can develop vacuum as high as 10⁹ mBar, which is equivalent to the pressure found in outer space.

Vacuum pumps

There are several types of vacuum pumps that are commonly used in vacuum technology, each with its own advantages and disadvantages. Some of the most popular types include:

1. Rotary Vane Pumps: work by using a series of rotating vanes to create a vacuum. Rotary pumps are reliable and cost-effective, but they have a limited vacuum range.
2. Scroll Pumps: use two interlocking scrolls to create a vacuum. Scroll pumps are oil-free and have a low noise level, making them ideal for use in cleanroom environments.
3. Roots Blowers: known as mechanical boosters, work by using two rotors that rotate in opposite directions to create a vacuum. Roots blowers can be used to boost the pumping speed of other pumps, allowing them to operate at lower pressures.
4. Turbo Pumps: are a type of kinetic pump that use a high-speed rotor to create a vacuum. Turbo pumps are ideal for achieving high vacuum levels and are commonly used in semiconductor manufacturing and other high-tech industries.
5. Cryogenic Pumps: use liquid nitrogen or helium to create a low-temperature environment that causes gas molecules to condense and freeze. The frozen gas is then removed from the vacuum chamber, creating a high vacuum. Cryogenic pumps are ideal for achieving ultra-high vacuum levels, but they can be expensive to operate and maintain.

In addition to the above-mentioned, there are also other specialized pumps such as ion pumps, getter pumps, and sorption pumps that are used in specific applications. The choice of a particular pump type will depend on the specific application, the required vacuum level, and the cost of the pump and its maintenance.

Apart from vacuum pumps, vacuum furnaces also incorporate advanced heating elements such as graphite, tungsten, and molybdenum, which can withstand high temperatures and prevent contamination of the workpiece. The heating elements are usually arranged in a way that allows for uniform heating of the workpiece, ensuring that the desired heat treatment process is achieved.

There are several types of vacuum furnaces, including batch-type, continuous, and hybrid vacuum furnaces. Batch-type furnaces are typically used for small-scale production, while continuous furnaces are suitable for large-scale, high-volume production. Hybrid furnaces combine features of batch and continuous furnaces and can be used for both small and large-scale production.