Metal 3D printing is a technology that belongs to digital thermal processing. The current 3D printing technologies for preparing metal mainly include selective laser melting and sintering (SLM and SLS), electron beam selective melting (EBSM), laser near-net shaping (LENS), etc. Compared with traditional processes, metal 3D printing has the advantages of direct shaping, no need for molds, personalized design and production of complex structures, high efficiency, low consumption, and low cost.
However, because of the material properties of metal 3D printing materials themselves, they all have specific application fields. Therefore, the process of selecting metal 3D printing materials involves weighing multiple factors. Moreover, 3D printing metal cannot be measured solely by the parameters of the metal 3D printer. Each metal material has its limit points suitable for its characteristics, including application, function, stability, durability, aesthetics, and economy. All designs have factors to consider.
Today, the metal powders used by metal 3D printers at home and abroad generally include tool steel, martensitic steel, stainless steel, pure titanium and titanium alloys, aluminum alloys, nickel-based alloys, copper-based alloys, cobalt-chromium alloys, etc.
1. Tool steel and martensitic steel
Taking tool steel and martensitic steel as an example, the applicability of tool steel comes from its excellent hardness, wear resistance, and deformation resistance, as well as its ability to maintain cutting edges at high temperatures. Mold H13 hot work tool steel is one of them, which can withstand process conditions of the uncertain time; martensitic steel, taking martensitic 300 as an example, also known as “maraging” steel, has high strength during the aging process; toughness and dimensional stability are all well known. They differ from other steels in that they are carbon-free and are intermetallic compounds, hardened by the metallurgical reaction of abundant nickel, cobalt, and molybdenum. Due to its high hardness and wear resistance, Martensite 300 is suitable for many mold applications, such as injection molds, light metal alloy casting, stamping, extrusion, etc. It is also widely used in aerospace, high-strength airframe components, and racing parts.
2. Stainless steel
Stainless steel is different from carbon steel in its current chromium content. 10.5% is the lowest chromium content in steel alloys. Stainless steel is not prone to rust or corrosion. Currently, there are three main types of stainless steel used in metal 3D printing: austenitic stainless steel 316L, martensitic stainless steel 15-5PH, and martensitic stainless steel 17-4PH.
Austenitic stainless steel 316L has high strength and corrosion resistance and can be used in a wide temperature range, down to low temperatures. It can be used in a variety of engineering applications, such as aerospace and petrochemicals, as well as in food processing and medical fields.
Martensitic stainless steel 15-5PH, also known as maraging (precipitation hardening) stainless steel, has high strength, good toughness, and corrosion resistance, and can be further hardened. It is ferrite-free. Currently, it is widely used in aerospace, petrochemical, chemical, food processing, papermaking, and metal processing industries.
Martensitic stainless steel (17-4PH) still has high strength and toughness up to 315°C and is extremely corrosion-resistant. It can bring excellent ductility to the laser processing state.
3. Alloy
The most widely used metal powder alloys for metal 3D printing materials mainly include pure titanium and titanium alloys, aluminum alloys, nickel-based alloys, cobalt-chromium alloys, copper-based alloys, etc.
1) Pure titanium and titanium alloys
Pure titanium currently used in the market, also known as commercially pure titanium, is divided into grade 1 and grade 2 powders. Grade 2 is stronger than Grade 1 and is also corrosion-resistant for most applications. Because pure titanium grade 2 has good biocompatibility, it has broad application prospects in the medical industry.
Titanium is the key to the titanium alloy industry. Currently, titanium alloys used in metal 3D printing are mainly titanium alloy grade 5 and titanium alloy grade 23. Because of their excellent strength and toughness, combined with their corrosion resistance, low specific gravity, and biocompatibility, they are widely used in aerospace and automobile manufacturing. It has very ideal applications and is used in the production of biomedical implants because of its high strength, low modulus, and strong fatigue resistance. Titanium alloy grade 23 has higher purity and is a divine grade of dental and medical titanium.
2) Aluminum alloy
Currently, there are two main types of aluminum alloys used in metal 3D printing: AlSi12 and AlSi10Mg. Aluminum silicon 12 is a lightweight additive for manufacturing metal powder with good thermal properties. It can be used in thin-walled parts such as heat exchangers or other automotive parts. It can also be used in aerospace and aviation industry-grade prototypes and production parts. Parts: The silicon/magnesium combination gives the aluminum alloy greater strength and stiffness, making it suitable for parts with thin walls and complex geometries, especially where they have good thermal properties and low weight.
3) Nickel-based alloy
In general, nickel-based alloys have good tensile resistance, fatigue resistance, and thermal fatigue resistance. At present, there are mainly Inconel 738, Hastelloy X, Inconel 625, Inconel 713, Inconel 718, etc.
Inconel 738 has good high-temperature creep rupture strength and hot corrosion resistance. It is a superalloy with a lower chromium content. It can be exposed to high-temperature corrosive environments up to 920–980 °C for a long time and is suitable for aircraft engines and gas turbines.
Hastelloy tanks, spray booms, exhaust pipes, afterburners, etc.; and because of its resistance to stress corrosion cracking, it is used in industrial furnaces, petrochemicals, and chemical process industries.
Inconel 625 still has good load performance under high-temperature conditions of about 815°C and has strong corrosion resistance. It is widely used in the aerospace, chemical, and power industries.
Inconel 713 has excellent thermal fatigue resistance and special breaking strength at 927°C, making it suitable for jet engine gas turbine blades.
Inconel 718 is a superalloy based on iron-nickel hardening. It has good corrosion resistance and resistance to heat, tensile, fatigue, and creep properties. It is suitable for various high-end applications, such as aircraft turbine engines and land-based turbines.
4) Cobalt chromium alloy
A cobalt-chromium alloy has high strength, strong corrosion-resistance, good biocompatibility, and non-magnetic properties. It is mainly used in surgical implants, including alloyed artificial joints, knee joints, and hip joints. It can also be used in engine parts fashion, the jewelry industry, etc.
5) Copper-based alloy
The copper-based alloy used in the market, commonly known as bronze, has good thermal conductivity and electrical conductivity, and can be combined with design freedom to produce complex internal structures and cooling channels, which are suitable for cooling more efficient tool insertion molds, such as semiconductor devices, and are also available It is a micro heat exchanger and has the characteristics of a thin wall and a complex shape.
The application fields of metal 3D printing materials are quite wide, such as petrochemical engineering applications, aerospace, automobile manufacturing, injection molds, light metal alloy casting, food processing, medical care, papermaking, power industry, jewelry, fashion, etc. I believe that with the continuous advancement of science and technology, the application of metal 3D printing materials will have an increasing impact on society in the future.
