While traditional forms of metal manufacturing like forging and casting have been around for hundreds of years, there are some applications where the best option is powder metallurgy manufacturing.
In this article, we’ll look at how powder metallurgy works, including which parts are best suited to the process. We’ll also go through the many powder metallurgy benefits you’ll enjoy.
What Is Powder Metallurgy Manufacturing?
Powder metallurgy refers to the material used to manufacture parts. This process uses a metal powder produced through a process called atomization, where molten metal is broken down by a high-speed spray of fluid or inert gas, then solidified into a powder as it cools.
The powder is then poured into a mold and compressed until it reaches the desired shape and density.
There are a number of ways you can adjust this process, of course. You can create alloys by mixing metal powders, and you can introduce a number of other materials as well, including abrasive surfaces, carbide tips, and materials intended to increase friction, which is the case when manufacturing brake pads.
Parts can also be sintered, which involves heating the parts to temperatures just below the melting point. This adds strength and durability and can also affect porosity, which is a vital element in manufacturing self-lubricating parts like bearings.
Powder metallurgy manufacturing combines flexibility and cost savings with high precision and accuracy, making it ideal for applications that otherwise might cost time and money you can’t afford to spend.
Ideal Parts for Powder Metals
While powder metallurgy manufacturing is not ideal for all use cases, there are many situations in which it is by far the superior technique. Typically, these parts tend to be smaller and more intricate, and they may have additional properties, like being magnetic.
Using traditional means of fabricating these small and more detailed parts would typically require a great deal of millwork. The sheer volume of the machining aside, maintaining consistency in all details on such intricate parts would be a challenge.
Instead, powder metallurgy allows parts to be fabricated as close as possible to their finished form, improving consistency while eliminating extra work.
Benefits of Powder Metal Manufacturing
There are a number of powder metallurgy benefits that you just can’t achieve when manufacturing metal components by other methods. Here are some of the most significant ways you could gain from this process.
Cost-Effectiveness
One of the most important powder metallurgy benefits that companies will notice is that the process is quite cost-effective. This is due to a number of factors, including the following.
Less Machining
Because parts are fabricated as close as possible to the final expected dimensions, there is very little machining that needs to be done in order to clean up the piece, saving both time and money.
Less Scrap
In other metal manufacturing processes, there’s usually a great deal of wasted product, and while much of that is reclaimed and recycled, each step in the recycling process costs money.
With powder metallurgy, most parts incorporate over 97% of the raw material, virtually eliminating waste. This is because powder metallurgy makes use of additive manufacturing principles, rather than subtractive manufacturing.
Scalability for High Volume
Powder metallurgy is an easily replicable process, which means that you can manufacture parts at a high volume. In fact, the most cost-effective use of this method is to produce more than 10,000 of each part per year!
Superior Finish
The powder metallurgy process produces an excellent surface finish on your final parts, and they can also have secondary finishes applied after sintering to add more resistance to wear or corrosion or to improve the part’s strength.
One of the other powder metallurgy benefits is its superior porosity compared to traditional methods. Because the manufacturing process determines the density of the final product, it is possible to create a more porous finish that will absorb lubricants, allowing you to create self-lubricating parts.
Unique Materials
Because powder metallurgy works by using a solid metal powder, it allows you to produce a wide number of unique parts with special properties that are difficult to replicate with other methods.
For instance, you can create a number of alloys that would be difficult or impossible to recreate with traditional methods, such as materials made for electrical contacts or metals with extremely high melting points.
One of the first uses for powder metallurgy was actually to create the tungsten blocks used to make incandescent light bulb filaments.
Powder metallurgy also lets you create products with specific characteristics. A large number of magnets are manufactured in this way.
Steel parts that are required to work at high speeds can benefit from the extra durability and performance they get from the powder metallurgy process, too.
It’s also possible to mix other materials into the powder during the manufacturing process. The linings of brakes, for instance, have non-metallic materials added during the powder metallurgy process that increase the friction of the surface. These materials are deeply embedded in the metallic matrix, ensuring that the friction properties can remain constant.
High-Performance Parts
This last point, the superior performance offered by powder metallurgy manufacturing, is one of the most important benefits offered by the process.
The sintering process provides excellent strength and durability for parts of all types, and the self-lubricating properties of some applications have become industry standards.
Powder metallurgy can also create components for use in airplane engines using nickel or cobalt superalloys. These alloys are not able to be replicated by other manufacturing techniques.
The tremendous precision the powder metallurgy process offers allows manufacturers to control the microstructure of every part to ensure proper performance within expected temperature ranges.
Looking for More Information About Powder Metallurgy Benefits?
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All manufacturing processes and technologies have their share of pros and cons. Yet, when it comes to powder metallurgy, few processes have changed for the better in a relatively short period of time.
Today, the advantages of powder metallurgy rival many conventional manufacturing technologies -- even machining -- when it comes to the production of high quantities. There are many angles to look at when comparing powder metallurgy vs. machining -- here are the seven most important:
7 Advantages & Disadvantages of Machining vs. Powder Metal
What are the advantages and disadvantages of CNC machining processes compared to powder metallurgy (PM)? While your project’s specific needs will play some role in that answer, we can still break things down across seven categories. Each will help you better determine which manufacturing process is best for your application:
Dimensional precision
Quality
Design flexibility
Affordability (tooling and per part)
Strength
Speed
Scrap efficiency
1. Precision
Powder metallurgy creates parts with little -- if any -- error. Your manufacturer has full microstructural control and can customize that microstructure to meet the specific needs of your application. Done correctly, it’s a net-shape part fabrication process that reduces or even eliminates the need for secondary machining. That saves time, energy, and costs throughout the manufacturing stage of product development.
Note that, on a part-to-part basis, PM can not provide the same dimensional precision of modern CNC machining.
Powder metallurgy does offer reliable part-to-part repeatability, which in part explains its popularity for large orders. Powder metallurgy tolerances depend on the material and processing your part requires.
Your small-component manufacturer will have to deal with a bit of distortion inherent to the thermal process every PM part undergoes. Since machining doesn’t involve sintering, it avoids this nagging issue.
A common axial flux stator made via soft magnetic composite (powder metallurgy), manufactured without machining.
2. Quality
Machining’s quality is dependent on the level of technology you’re using. CNC quality is nearly unmatched; manual machining not so much. If you have access to advanced software and understand CNC machining design guidelines, you can easily match specifications of complex parts.
Not only is the quality of powder metal parts high, you can also take your part’s properties a step further with advanced materials. While most powder metal parts are made from a traditional iron-carbon-copper mix, there’s an abundant array of alternatives available that offer enhanced properties.
Potential additives include:
These metals, along with processing steps exclusive to powder metallurgy, can add:
One limitation of the conventional machining process is you can't just throw multiple materials in a blender and get the best properties of both worlds.
Furthermore, machining of hard materials can prove difficult (i.e. stainless steel). What about the machinability of powder metallurgy steel parts, as part of secondary finishing? It's generally a non-issue,. although soft magnetic composites (a material group dedicated to magnetic performance) are usually too brittle to machine.
3. Design Flexibility
Powder metallurgy is an “additive” process, which means that design starts from scratch instead of from a slab of material. With the ability to create from the ground up, you can achieve advanced part designs in an instant. Powder metal gives you the ability to use geometries that would be difficult or wasteful in design for CNC machining.
Even so, there’s a limit to net-shape forming with metal powder. The axial compression delivered by a punch moving into the die means your power metallurgy manufacturer can’t form some features. Either the powder won’t be moved into die, or if it does, release of the part afterward becomes difficult or even impossible. These features include:
However, those features can be added later with machining services.
One of the unique aspects of powder metallurgy is the ability to form helical gears. Most helical gears are in the 20° angle range. PM can mold helical shapes up to 35° -- with zero waste. And, in some of the most advanced powder metallurgy processes, you can even form cross-holes.
4. Affordability (Tooling & Per Part)
Cost-effectiveness is the predominant reason OEMs request powder metallurgy services. PM wins the cost competition vs. machining thanks to:
Elimination of process steps
More efficient material use (more on that below)
Potential lower energy consumption per component produced vs. starting material, when you factor in material losses due to machining
Ability to make complex shapes that conserve material
One of the disadvantages of powder metallurgy is that short product runs are a poor fit thanks to per-part costs and tooling costs. For tiny production runs, CNC machining remains a more affordable option. CNC machining requires no tooling costs.
5. Strength
Machining operations can produce parts from materials that take on high tensile forces and impact loads. Today’s machine shops work with some amazingly high-performing materials.
Powder metal parts by nature aren't as strong as machined parts. Why? They have tiny holes, aka porosity.
Keep in mind that powder metal parts can be stronger than you think thanks to advanced sintering technology. Sintering may give your part an acceptable level of strength while allowing you to take advantage of powder metallurgy’s many other advantages over machining.
6. Speed
Powder metal, like cupcakes, is better when the batch is large.
For short-run orders, you may be better off with conventional machining. A machined part only takes a few weeks total. It doesn’t take much effort to put a piece of bar stock in the CNC milling machine and start whittling away.
But once you have a tool in place, that's when powder metallurgy suppliers begin to shine. It’s infinitely better than high-volume-production CNC machining, which requires a lot of:
Reprogramming
Retooling
Labor hours
One of the benefits of prototyping with powder metallurgy over prototype CNC machining is that tooling costs are a one-time investment. If prototype tooling is successful, it carries the added value of being usable throughout final production.
(Related Resource: Prototyping Motor Components With SMC Powder - Benefits vs. CNC Machining Prototype Manufacturers)
7. Scrap Efficiency
Engineers have wondered for years how to best reduce scrap in machining operations.
Powder metallurgy makes far more efficient use of its raw materials -- we’re talking 3% scrap rates. Meanwhile, machining parts can result in 50% material waste. Because the powder metallurgy process is an additive one, your manufacturer only needs as much material as your design requires.
The world now recognizes powder metallurgy as maybe the most sustainable metal manufacturing process, and a model of how to reduce material waste in manufacturing.
While machining scrap can be recycled, these operations still account for significant material costs, much of which is discarded.
The Winner Is … (and More Debate)
There’s no need to start your project with that depressing thought of, “How much material am I paying for that’s going to get thrown away?” Instead, with the right powder metal process, you can dream of the endless design and cost-cutting possibilities you’ve opened up.
The free e-book below reveals more about the pros and cons of powder metallurgy vs.:
CNC machining
Stamping
Casting
Forging
MIM -- and more
Don’t miss the chance to discover a cost-cutting or performance-boosting trick you never knew existed!
(This article was originally published in June 2022 and was recently updated)