Can post-processing improve the performance of metal 3D printed parts?

1. Heat treatment: get rid of flaws and make the organisation work better
When metal 3D printing happens, quick cooling can generate residual stress, coarse grains, and compositional segregation inside the material. This can easily cause the parts to bend or shatter. By managing the heating, insulating, and cooling processes, heat treatment can greatly improve the qualities of materials.
tension reduction annealing gets rid of any tension that was left over from the printing process and stops pieces from changing shape when they are used again. After stress relief annealing, GE aircraft was able to minimise the distortion of 3D printed titanium alloy fuel nozzles by 80%, which met the strict standards for dimensional stability in aircraft engines.
Solid solution annealing and ageing treatment: This process makes materials stronger and tougher by breaking down detrimental phases and forming strengthening phases. After a particular company used solution annealing and ageing treatment, the tensile strength of 3D-printed Inconel 718 high-temperature alloy parts went up from 900MPa to 1200MPa, and the fatigue life went up by three times.
Hot isostatic pressing (HIP): Getting rid of internal pores and microcracks under high temperature and pressure, which makes the material density almost 100%. The fatigue strength of the Airbus A350's titanium alloy flexible shaft went up from 450MPa to 620MPa after HIP treatment, which meant it passed the 20-year design life certification.
2, Surface treatment: making it last longer and work better
The roughness of the surface of 3D printed parts is usually between 5 and 10 μm, which can readily become places of stress concentration and make the parts less resistant to fatigue. Surface treatment enhances surface quality via physical, chemical, or mechanical techniques, while imparting further functions:
Mechanical polishing: Use tools like sandpaper and grinding wheels to smooth out rough spots on the surface and bring the roughness down to below Ra 0.8 μ m. BMW Group mechanically polished the 3D-printed aluminium alloy water jacket, which made the surface roughness go down from Ra 6.3 μ m to Ra 0.4 μ m and the fatigue life go enhanced by 40%.
Shot blasting and sandblasting: Using fast-moving sand to hit the surface and generate a layer of compressive stress that stops cracks from spreading. After a particular company used shot peening treatment to 3D print titanium alloy aviation connections, its high cycle fatigue The life span went from 10 ⁵ cycles to 10 ⁷ cycles.
Chemical plating and electroplating: putting metal or alloy coatings on the surface to make it more resistant to wear and corrosion. In the medical device industry, 3D-printed cobalt chromium alloy artificial joints have been chemically plated with nickel and phosphorus. This has increased their resistance to salt spray corrosion from 240 hours to 1000 hours, which meets the long-term clinical needs.
Anodising: Using electrochemical processes to create an oxide film on the surface of aluminium alloy to make it look better and protect it from corrosion. After anodising, the surface hardness of 3D-printed automobile wheels from a certain company went from HV 150 to HV 350, and their resistance to scratches improved by five times.
3. Precision machining: getting high accuracy and functional integration
Most of the time, 3D printed products have a tolerance of ± 0.076mm, which makes it hard to meet the needs of areas like aerospace and precision instruments that need ± 0.025mm accuracy. Using technologies like CNC and electrical discharge machining (EDM), precision machining can make the following improvements:
Control of dimensional accuracy: GE Additive Manufacturing uses CNC machining to improve the accuracy of 3D-printed titanium alloy parts from ± 0.076mm to ± 0.025mm, which is what is needed to put together important parts for aircraft engines.
Making complex features: Electrochemical machining (ECM) uses electrochemical reactions to break down materials. It may also work on thin-walled, deep cavity structures that are hard to do with other technologies. Using pulse electrochemical machining, Voxel Innovations makes the walls of 3D-printed chromium nickel iron alloy turbine blades thinner, from 1.2mm to 0.8mm, and the surface roughness smoother, from Ra 3.2 μm to Ra 0.4 μm.
Integration of functions: Post-processing can make it possible to combine several materials and procedures into one. For instance, one company used 3D printing, CNC machining, and electroplating to combine 7 elements into one gearbox shaft. This cut the weight by 30% and the cost by 40%.
4. Industry case: Post-processing leads to a big improvement in performance
In the aerospace field, the Airbus A350's titanium alloy flexible shaft uses 3D printing, HIP processing, and CNC machining to create a part that can last for 20 years and is the first 3D printed major load-bearing component to receive airworthiness certification.
Johnson & Johnson's 3D-printed cobalt chromium alloy hip cups for medical equipment have been sandblasted and plated with electroless nickel phosphorus, which gives them a fatigue life of more than 95% of forged parts. There have been more than 100,000 cases where they have been put in.
The titanium alloy control arm of the Tesla Cybertruck uses 3D printing, quenching and tempering, and mechanical polishing technology. This makes it 20% stronger and 15% lighter, making it a model for high-performance electric vehicles.