Do all metal 3D printed parts require heat treatment?

1. The main job of heat treatment is to get rid of flaws and make things work better.
Heating, insulating, and cooling processes can greatly improve the microstructure of metal 3D printed parts by heat treatment. This makes the parts work better overall.
Getting rid of residual stress: Uneven cooling and solidification during printing can easily cause residual stress inside the pieces, which can cause them to bend or shatter. Slow cooling throughout the annealing process might help relieve stress. After annealing, for instance, the stress reduction rate of aerospace structural parts might be more than 80%.
Enhancing mechanical properties: Quenching and tempering together can make things much harder and stronger. For instance, after quenching, 316L stainless steel is 30% harder and more resistant to wear, making it good for mechanical parts that have to carry a lot of weight.
Grain refinement: The directional recrystallization process manages the thermal gradient to fuse tiny grains into columnar crystals. This makes the material better able to resist creep at high temperatures. MIT research indicates that after directional recrystallization treatment, the grain size of nickel-based high-temperature alloys grows by several orders of magnitude, and the creep life lasts much longer.
Treatment for densification: Hot isostatic pressing (HIP) gets rid of internal pores by using high temperature and high pressure. This makes the material density almost 100%. For instance, HIP treatment has enhanced the low cycle fatigue life of turbine discs in aircraft engines from 5000 cycles to 20000 cycles.
2. Situations without heat treatment: improving material characteristics and processes
Even though heat treatment has a lot of benefits, components can be utilized right away without any extra work in the following situations:
Parts that don't need a lot of stress: If the part structure is basic, the size is modest, and it doesn't care about residual stress, you don't need to anneal it. For instance, minor decorative or non-load-bearing structural parts are not likely to distort and do not make heat treatment worth the money.
Different combinations of materials and processes: Some materials have created perfect microstructures while being printed. For instance, the electron beam selective melting (EBSM) technique cools down more slowly, which means that titanium alloy (Ti6Al4V) printed parts don't get as coarse, which is good for medical implants because they need to be biocompatible.
Scenario for giving attention to surface quality: If the part needs to be very smooth, heat treatment could cause it to oxidize or change shape. At this point, heat treatment can be replaced by surface treatment methods including chemical polishing and laser polishing. After electrochemical polishing, the surface roughness of porous titanium alloy implants drops from 6–12 μm to 0.2–1 μm without the need for any more heat treatment.
Verification of rapid prototyping: Heat treatment might make the development cycle longer at the product design stage. For instance, the integrated flexible hinge in the consumer electronics area needs its prototype parts to be made quickly, and employing printed parts directly can speed up the verification process.
3. A framework for making decisions: Finding the right balance between performance, cost, and efficiency
A thorough look at the following variables is needed to decide whether or not to do heat treatment:
Functional requirements: Aerospace parts must be able to handle tremendous temperatures and strains, which is why heat treatment is important.
Medical implants need to be strong and safe for the body, and annealing or HIP treatment can help them work better.
If the only thing that matters is how the art sculptures or display pieces look, heat treatment can be skipped to save money.
Nickel-based high-temperature alloys are likely to crack, thus they need solid solution and aging treatment to make them tougher.
Parts made of aluminum alloy (such AlSi10Mg) contain microscopic grains, which makes them lightweight right away.
Type of process: The powder bed melting (PBF) process needs to be annealed since it cools down quickly and leaves a lot of tension behind.
Because it has a high heat input and low stress level, the directed energy deposition (DED) technique cuts down on the need for heat treatment.
Cost limits: HIP equipment is expensive to buy and run, which makes it hard for small and medium-sized businesses to afford. They need to find a compromise between performance and cost.
Heat treatment of complicated structural components might cause them to change shape. To avoid this, simulation optimization should be used to support design and raise research and development expenditures.