What Is Powdered Metal For Additive Manufacturing？

In today’s manufacturing revolution, the Metal Powders For Additive Manufacturing has become a key force driving technological progress. From aerospace to medical devices to high-performance industrial components, metal powders are not only materials, but also a source of innovation. Compared with traditional processing methods, metal powder combined with Additive Manufacturing technology brings us unprecedented design freedom, material utilization and performance controllability. This article will give you an insight into what metal powders are, how they are manufactured, and the central role they play in additive manufacturing-from principle to application, from material to future.

What is Powdered Metal?

We often say “powder metal”, or more specialized term “metal powder”, in fact, refers to those materials composed of extremely small metal particles. These particles can be as small as a micron in size and are almost indistinguishable to the naked eye. Imagine grinding a piece of hard metal into a powder finer than sand, which is probably what it means. It is the cornerstone of the Powder Metallurgy process and a key raw material for the additive manufacturing we are talking about today.

Compared with the traditional casting, forging these familiar processes, powder metallurgy has its unique advantages. For example, it can produce parts with extremely complex shapes and high precision requirements, and the material utilization rate is very high, which greatly reduces waste. This is undoubtedly a huge improvement in cost control and sustainable development.

Composition and Classification of Metallic Powders

There are many types of metal powders, we can simply divide them into several categories:

• Pure metal powder: this kind of powder is mainly composed of a single pure metal, such as our common iron powder, copper powder, aluminum powder and so on. They each retain the inherent characteristics of pure metals and are suitable for applications that have specific requirements for single metal properties.
• Powder Alloy: Alloy powder is made by mixing or fusing two or more metal elements in a specific ratio. By skillfully selecting different metal elements and their proportions, we can prepare alloy powders with various excellent properties, such as high strength, corrosion resistance, high temperature resistance and so on. It can be said that alloy powder has opened the door for us to customize the properties of materials.
  • Pre-alloyed powders versus mixed powders: Among alloyed powders, we also distinguish between pre-alloyed powders and mixed powders. Pre-alloyed powder is prepared by fusing various elements together to form an alloy and then making powder; while mixed powder is made by mixing different pure metal powders in proportion. In practical applications, the properties of pre-alloyed powders are usually more stable and uniform.

Why metal powder is so important

Some people may ask, why is powdered metal? This is going to start from its unique point of view. The key reason why metal powder plays an indispensable role in additive manufacturing is its unique physical and chemical properties:

1. High specific surface area: The smaller the particle, the larger the overall surface area. This makes it easier for the metal powder to diffuse and combine during the sintering process to form a dense part.
2. Shape freedom: This is a core advantage of additive manufacturing. By precisely controlling the accumulation and melting of the powder, we can “print” any complex structure we can think of, which is beyond the reach of traditional manufacturing processes.
3. Material diversity: Whether it is a pure metal or a variety of high-performance alloys, it can be applied to additive manufacturing in powder form, which greatly expands the range of materials to choose from.
4. Controllability of performance: By adjusting the particle size, morphology, composition of the powder, and subsequent process parameters, we can precisely control the microstructure and macroscopic properties of the final part.

In my opinion, metal powder is not only a raw material, but also a bridge connecting design and implementation, and the wings of additive manufacturing technology to take off. Without these fine metal particles, what we see today

The Production of High-Quality Metal Powders

The main preparation method of metal powder

Making high-quality metal powders, especially those suitable for additive manufacturing, is no simple task. There are several mainstream methods on the market, each with its own unique principles and applicable scenarios.

• Atomization: There is no doubt that atomization is the optimal method for additive manufacturing of metal powders. Its core idea is simple: turn molten metal into tiny droplets, and then let them solidify into powder during the cooling process.
  • Gas atomization: In my opinion, this is currently the most mature and widely used method. The principle is that high-pressure inert gas (such as argon or nitrogen) is used to impact the molten metal stream at high speed to disperse the metal into very small droplets. These droplets rapidly cool and solidify in the gas, eventually forming a powder with a very good sphericity. The advantages of gas atomized powder are obvious: the sphericity is good, which means that the powder has excellent fluidity, and a uniform and dense powder layer can be formed when the powder is spread; the purity is high, and the inert atmosphere effectively avoids the introduction of impurities such as oxidation. In my many years of experience, whether it is SLM (Selective Laser Melting) or EBM (Electron Beam Melting), gas atomized powder is the first choice. Its stability and controllability are the key to ensure print quality.
  • Water Atomization: In contrast to gas atomization, water atomization uses a high pressure stream of water to break up the molten metal. This method usually results in irregularly shaped powders. Although not as flowable as a spherical powder, it is relatively inexpensive to produce and still has value in certain applications such as binder jetting (Binder Jetting) that require a high specific surface area or a specific shape. However, for our mainstream SLM/EBM process, water atomized powder is not enough.
• Electrolysis method: This method mainly deposits metals by electrolyzing solutions containing metal salts. It can produce high purity powder, but usually the powder shape is irregular, and the particle size is coarse. In my opinion, although electrolysis has its place in the field of traditional powder metallurgy, its application in additive manufacturing is relatively limited, and it is more as a supplement to the preparation of some special alloy powders.
• Reduction method: The reduction method is mainly to reduce the metal oxide to metal powder with a reducing agent (such as hydrogen, carbon) at high temperature. The powder produced by this method is usually spongy or irregular, with high porosity and relatively wide particle size distribution. In additive manufacturing, reduced powder is not the mainstream, because it is difficult to meet our strict requirements for powder morphology and fluidity.

Effect of Powder Properties on Additive Manufacturing

The quality of the powder determines the upper limit of the printed part.

• Particle morphology: The spherical powder has excellent fluidity, which can ensure the formation of a uniform and dense powder layer during the powder spreading process, reducing voids and defects. This is directly related to the density and mechanical properties of the printed parts. Irregular powder will greatly reduce the fluidity, resulting in uneven powder spreading, and may even block the powder feeding system, which we try to avoid. The bulk density of the powder is also closely related to the morphology. Higher bulk density means that more metal can be accommodated in the same volume, which has a positive effect on improving printing efficiency and part density.
• Particle size distribution: Particle size distribution affects the layer thickness during printing and the surface finish of the final part. Too coarse powder may limit the minimum layer thickness we can print and affect the expressiveness of details. Too fine powder, although conducive to surface finish, but too fine powder in the laser or electron beam under the action of easily splash, affect the forming stability. Therefore, an optimized and narrow particle size distribution is our ideal state, which can take into account the uniformity of powder spreading, the stability of printing and the surface quality of the part.
• Chemical composition and purity: this cannot be overemphasized. The chemical composition of the powder directly determines the material properties of the final part, such as strength, hardness, corrosion resistance, and so on. Any minor deviation in composition may result in substandard part performance. High purity is the hard index of additive manufacturing, impurity elements, especially non-metallic inclusions, will become the stress concentration point inside the part, causing cracks, seriously affecting the fatigue life. This is the link that I most often encounter in the project and need to be strictly controlled.
• Oxygen content control: in particular to mention the oxygen content. In my opinion, oxygen content control is one of the most critical characteristics of additive manufacturing metal powders. Metal powder may be oxidized in contact with air during production, transportation, storage and even printing. Excessive oxygen content will not only reduce the fluidity of the powder, but also form oxide inclusions during the printing process, which will seriously weaken the mechanical properties of the parts, especially the plasticity and toughness. For some active metals such as titanium alloys, it is necessary to control the oxygen content at a very low level. Therefore, the monitoring and protection of oxygen content from production to use is the key to the success of additive manufacturing.

The Role of Specific Metal Powders in Additive Manufacturing

In the world of additive manufacturing, metal powder is undoubtedly the core “building material”. We usually say “powder steel” or “steel powder”, in fact, covers many different types, each has its own unique properties and applications.

Let’s talk about stainless steel powder first. This is one of the most widely used powders in my opinion. For example, 316L stainless steel powder has very good corrosion resistance, high precision of printed parts and good surface finish. Therefore, in the aerospace field, some structural parts that require corrosion resistance, and in medical devices, such as surgical instruments or some implants, 316L has performed well. Another commonly used is 17-4PH stainless steel powder, which can achieve high strength and hardness after heat treatment, while maintaining a certain degree of corrosion resistance, so we often use it in some high-performance components.

This is followed by tool steel powder. When you need to make a mold or some wear parts, tool steel powder is particularly important. This kind of powder printed parts, its high hardness and excellent wear resistance is the traditional manufacturing process is difficult to match. Imagine how difficult it was in the past to form an injection mold with a complex structure through additive manufacturing. There is also high-speed steel powder. Although it is not as widely used as stainless steel, it still occupies a place in cutting tool manufacturing. It allows the tool to maintain hardness and sharpness during high-speed cutting and improve processing efficiency.

In addition to these, of course, there are other key metal powders, which play an irreplaceable role in their respective fields:

• Titanium alloy powder: If there is any material that can perfectly combine biocompatibility, high strength and lightweight, it must be titanium alloy. In medical implants, such as orthopedic implants, dental implants, titanium alloy powder is the first choice. At the same time, in the field of aerospace, its lightweight characteristics are essential to reduce the weight of the aircraft and improve performance.
• Nickel-based superalloy powder: This is the material specifically designed for extreme high temperature environments. In gas turbine components, such as turbine blades and combustion chamber components, nickel-based superalloy powder printed parts can withstand extremely high temperatures and stresses while maintaining excellent corrosion resistance. This is of great significance for improving engine efficiency and life.
• Aluminum alloy powder: lightweight is the eternal pursuit of modern industry, aluminum alloy powder is undoubtedly an important boost on this road. In the automotive and aerospace industries, aluminum alloy powder provides great design freedom for structural parts with high lightweight requirements.

Looking to the future, the development direction of metal powder for additive manufacturing is becoming more and more diverse. We have seen the application of composite powders, which combine the advantages of two or more materials to create materials with superior performance. In addition, the functional gradient material powder also has the potential to make different areas of the part with different material properties, so as to achieve more complex and optimized functions.

Advantages of Powder Metallurgy in the Age of Additive Manufacturing

The rise of additive manufacturing has undoubtedly brought new vitality to the traditional technology of powder metallurgy. When we talk about additive manufacturing, in fact, a lot of times we are talking about the broad scope of powder metallurgy. The combination of the two, the advantages are subversive:

Precision and complexity:

This is one of the most striking features of additive manufacturing, and its core driving force is metal powder. Traditional manufacturing processes, such as casting, forging, or machining, are often inadequate or even impossible to manufacture parts with complex internal structures, bionic geometries, or microchannels. But with additive manufacturing, we can accurately print every pixel in a 3D model.

Imagine structural parts that require lightweight and high performance in the aerospace field, or implants that need a perfect fit with the human body in the medical field. Their design freedom is infinitely amplified by the combination of powder metallurgy and additive manufacturing. I remember once, we successfully printed a turbine blade with complex cooling channels inside, which was almost impossible in the past.

High material utilization:

Traditional subtractive manufacturing generates a large amount of chips and scrap, especially when processing expensive or difficult to process materials, and material costs can rise sharply. Additive manufacturing, on the other hand, is the addition of material, and its basic principle is to melt or sinter powder on demand, thereby significantly reducing material waste.

Unused metal powder can usually be recycled, which not only reduces production costs, but also meets the current global pursuit of sustainable development. The advantage of high material utilization is even more pronounced for materials that are inherently expensive, such as nickel-based superalloys or titanium alloys.

Performance optimization:

 By precisely controlling the composition of the metal powder, the particle size distribution and the process parameters during additive manufacturing (such as laser power, scanning speed, layer thickness), we are able to obtain unique properties that are difficult to achieve with conventional methods. For example, the grain structure of an additive-manufactured part can be finely controlled, and sometimes even a unique non-equilibrium state structure can be formed, which gives the material greater strength, toughness, or corrosion resistance.

 A common example is isotropy. Conventional forged or rolled parts tend to have distinct anisotropy, that is, different mechanical properties in different directions. Whereas additive manufacturing, by stacking layer by layer, can effectively reduce or even eliminate this anisotropy if the process is properly controlled, so that the parts exhibit uniform and excellent performance in all directions. This uniformity is essential for critical components working in complex stress environments.

Cost-effectiveness:

When it comes to cost, there is often a misconception that additive manufacturing must be expensive. Indeed, the cost per piece may be higher than for mass-produced traditional parts. However, powder metallurgy combined with additive manufacturing has demonstrated unparalleled economics in scenarios where small batches, customization, or the production of highly complex parts are needed.

First of all, it eliminates the need for traditional manufacturing of a large number of mold, fixture investment, shorten the product development cycle. Secondly, due to its high degree of design freedom, multiple functions can be integrated in one part, reducing assembly links and further reducing the total cost. Additive manufacturing is undoubtedly the best choice for parts with short life cycles, fast replacement, or prototypes that require rapid iterative optimization.

New material development:

Powder metallurgy provides a broad and efficient platform for the development of new alloy materials. We can prepare alloy powders with special composition and microstructure by mixing powders of different compositions, or by gas atomization, and then use additive manufacturing technology to quickly verify its performance.

This ability to quickly try and error has greatly accelerated the progress of materials science. For example, some high-entropy alloys that are difficult to achieve with traditional casting, or functional materials that require a gradient composition distribution, can be easily achieved through additive manufacturing technology. It’s not just about making existing materials, it’s about creating the materials of the future.

Conclusion:

In general, metal powders for additive manufacturing is not only the manufacturing material, but also the core driving force for modern industrial innovation. It makes complex structural design, lightweight, high performance and customized manufacturing a reality. From stainless steel to titanium alloys, from aerospace to medical implants, metal powders are changing the logic of product design and production in ways never before seen. With continuous advances in pulverizing technology, powder purity control, and additive manufacturing processes, the potential of metal powders continues to be unleashed. In the future, it will continue to lead the manufacturing industry to develop in a more efficient, smarter and more sustainable direction, providing a solid “material foundation” for the era of industrial 4.0 “.