An introduction to powder metallurgy

An introduction to powder metallurgy

This article will introduce one of the most important metal manufacturing processes in today's world: powder metallurgy. We will learn a little about the basics of powder metallurgy techniques, how they work, and some of the technique's major benefits. Hopefully, the end result will be a better understanding of how sintering and other metallurgy solutions can help you achieve your industrial goals.

What is Powder Metallurgy?

Powder metallurgy is a technique used across the world to process metallic powders into useful materials. Thanks to its extreme versatility, powder metallurgy is becoming ever more popular across all global markets.

At its simplest, the technique involves using specially formulated powders, which are compressed and subsequently sintered in vacuum furnaces. This causes the powders to chemically bond, producing alloys which can have a wide range of properties, depending on the industrial task involved.
Recent years have seen powder metallurgy experience a surge in popularity, relative to alternative metallurgical techniques such as die casting.
The reasons are simple: powder metallurgy allows users to create high-quality components, while near-net-shape dimensional control provides a high degree of control over the manufacturing process, facilitating the production of complex shapes.

Different Technologies that involve Powder Metallurgy

Now let's expand things a little, by introducing some of the main types of powder metallurgy. There are three major variants of powder metallurgy, and each has their own specific applications. These techniques are as follows:

  • Conventional Press and Sinter Powder Metallurgy (PM)
  • Additive Manufacturing (AM)
  • Metal Injection Moulding (MIM)

The technique users choose generally depends on their needs and budget.

Additive manufacturing is also less suitable for mass production, but is highly suited to bespoke metallurgy, so is regularly used by artists and engineers working on one-off projects, where costs are less important than quality. By contrast, standard powder metallurgy can be integrated into mass production systems relatively cheaply.

Looking at Powder Metallurgy in More Detail

Of the four types of PM listed above, there are a couple that we are really keen to highlight: conventional vacuum sintering (PM), and Additive Manufacturing (AM).

Firstly, vacuum sintering involves using a vacuum furnace to generate high temperatures to chemically compact and densify metallic powders, resulting in products with the properties that users require.
Vacuum furnaces
are preferred, because they reduce the risk of oxidation, resulting in more even atomic diffusion and more reliable results. Before the sintering phase, it is always necessary to debind components, preparing them for processing. As debinding generates potentially damaging waste gases, sintering furnaces will often be independent of debinding equipment. However, vacuum debinding can integrate the two processes.
Any workshops using vacuum sintering will need to decide which method to use.

Additive Manufacturing could be seen as an updated version of conventional sintering.
In a similar way, it involves manufacturing powders into the desired shape, then applying heat to give them the correct properties, but there are some significant differences.
In AM systems, die moulding of metallic powders is replaced by cutting edge techniques. This could include laser metal fusion, electron beam melting, or selective laser melting. In any case, these processes generate the finished result from digital images, which are often created using CAD packages. This has made AM very popular among architects or product designers, who use it to create prototypes for their designs. But it is becoming ever more popular among high-end manufacturers who rely on custom-formed components.

It's also important to note that both of these processes don't use metal powders alone. One of the great strengths of powder metallurgy is the way that other materials can be incorporated into the process.
These include advanced composite and ceramic materials.

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What are the Advantages of Powder Metallurgy?

Now that we know about the most important types of PM, let's look in more general terms at what this technique has to offer.
When we look at PM in more detail, we see that it has many advantages over these techniques.
Most importantly, powder metallurgy ensures a high level of precision. Alloy powders are compacted in a die into the correct shape, then sintered in precisely calibrated furnaces, where they chemically bond. This results in a high degree of uniformity in the shapes produced, and in many cases very little machining is needed after that point. In fact, there are some shapes which can only be reliably manufactured using powder-based metalworking techniques. These could include radial projections, parts with unusual curvature, or eccentric elements.
Generally speaking, if a metal part requires irregular notches, slots or curves, it will be easier to use powder metallurgy to achieve the desired shape than by using standard machining techniques.

PM users are therefore able to expand the range of shapes they are able to process.
But there are other ways that this technique makes it easier to customise metalworking processes. By using powder metallurgy, technicians can control properties like porosity and tailor densities, strength and heat resistance.
At the same time, the process is highly repeatable, while generating minimal amounts of waste. So it's easy to see why PM is being embraced worldwide.

Understanding Whether to Use Powder Metallurgy or Not

Now let's try to offer some advice to companies who are considering whether to implement a powder metallurgy-based manufacturing solution. Despite the qualities we noted above, it's still true that not all metal formation tasks are appropriate for PM, and choosing the correct type of PM is also critical. It might help to think about a few criteria to consider while you make your decision.

  • Cost - PM can deliver reduced processing costs in some situations.
    This is generally true where users require an optimal lifecycle performance, and where the components produced will be used in conditions involving extreme heat or corrosion. In these cases, PM can create components with impressive durability and reliability. That's why it is often used for manufacturing parts like saw teeth for industrial machinery, or aviation components.
  • Narrow tolerances - Secondly, PM can be an excellent solution when you need to manufacture parts to very narrow tolerances.
    This applies whether the parts in question are simple or extremely complex, and it is possible to produce most pieces without a drastic increase in costs or quality. So if you are comparing precision casting techniques to powder metallurgy, PM can often be the right way to go.
  • Sustainability - Powder metallurgy is also a more environmentally friendly metal processing technique than options like casting and machining.
    Because of its net-shape capabilities, PM ensures very low waste levels when shaping components, helping companies hit their environmental targets.

So, when you assess the right technique for your next metal production challenge, it's a good idea to bring powder metallurgy into the equation. With its cost effectiveness, low waste levels and precision, it would be an appropriate solution for numerous industrial organisations.

How Have Industrial Manufacturers Used Powder Metallurgy?

Industrial manufacturers across the world are constantly coming up with new ways to use PM. That's not a surprise, because the technique would be a neat fit for almost any situation where manufacturers desire minimal waste and a high degree of control.

Here are a few recent examples of how PM has been integrated into global manufacturing chains:

  • Automotive gears - PM is now a go-to technology for leading car makers, as its cost has declined compared to cast-finished steel or iron varieties.
    PM works well with helical, bevel and spur type gears, and has also been used to create gears for everything from tractor transmissions to heavy-duty oil pumps. Manufacturers love it because of its precision and efficiency, but also because it allows them to minimise the weight of their gears without losing strength.
  • Turbine discs - PM has also been incorporated into the aerospace and power production sectors.
    HIP in particular has become a regular part of jet engine production, and will commonly be used to manufacture gas and wind turbines, often featuring nickel super-alloys, as well as titanium components.
  • Medical devices - The healthcare sector has benefited from PM's development, especially in the production of small-scale precision components.
    So you'll now find PM-made parts in all kinds of medical tools and equipment, delivering reliable performance and saving lives.

Choose the Ideal Metallurgy Solution For Your Needs

If you need to create precision-engineered components with high strength, corrosion resistance and heat tolerance, and you want to minimise the need for machining and waste, powder metallurgy could be the right solution.

While additive manufacturing is the most specific, tailored approach available, conventional powder metallurgy (or vacuum sintering) continues to offer a viable and cost effective production option.
So think about which method works best for your unique needs.

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