If you’re considering forged parts for your manufacturing and assembly needs, you probably know that closed die forging, also known as impression die forging, is a popular solution.
But when you’re trying to maximize performance while keeping costs down, it’s important to consider all your options.
Today, by introducing advances such as ultra-high temperature sintering combined with non-traditional PM alloys, mechanical properties of these components now approach the levels of their wrought steel or forged counterparts.
Powder metallurgy (PM) press and sinter technology offers a competitive alternative to closed die and powder forging applications. The advantages of powder metallurgy can deliver even better part-to-part uniformity, less tooling cost, and maybe an ideal solution for your needs.
What Is Traditional Forging and Why Do People Use It?
Forging can’t be defined as a single process -- there are a variety of forging processes, some of which are more efficient and precise than others.
- Open die forging - a methodology for shaping a green ingot without any die structure. Heat it and beat it!
- Closed die forging - the most well-known forging process. It’s the one shown in movies, where white hot steel is transferred into a series of shaped dies and then formed via numerous press strikes into a shape with plenty of flash and sparks.
- Precision die forging - the next iteration of closed die forging, where instead of throwing flash, you can construct a near-net shape.
- Powder forging - a derivative of precision die forging, but instead of starting with a steel blank, you start with a sintered PM shape and forge a near-net-shaped component without flash.
Forging applications have been around for a long time, and are how many high-volume parts are manufactured today. However, it’s not the most efficient process, and it begs the question: Is there a better method?
The answer, in some cases, is yes. New developments in unique alloy design, advanced compaction, and ultra high-temperature sintering for PM components allows us to take PM to a new level of mechanical property performance.
With these new methods, you can approach the performance of precision die forging but with the additional benefits of PM, such as closer dimensional control and better tool life. Let’s dive in:
The PM Alternative
Let’s talk about what conventional powder metal is able to achieve. Recent advances in PM technology have allowed it to offer:
- More complex shape-making capabilities
- Reduced tooling and part cost
- Low scrap waste - powder metallurgy is a green technology!
Now, let’s consider traditional forging.
For the most part, closed die forged parts are simple shapes, either one- or two-level shapes like gear blanks. PM is capable of advanced shape-making for multi-level parts without additional processes like machining.
And finally, by combining methods like ultra-high temperature sintering with unique alloys, powder metallurgy manufacturers can create custom materials to fit many component design needs. Despite all these great advances in PM technology, some parts might not be suitable for even these advanced materials and processes, and for that, PM forging is an option.
PM forging utilizes the same benefits of conventional powder metal with the added step of hot forging to create a net or near-net shape part while still maintaining the many fundamental advantages of PM.
Does PM Technology Make Traditional Forging Applications Irrelevant?
The short answer to that question is, no, not for every application. Traditional forging still has advantages for certain components, but PM now offers an alternative to some applications.
Manufacturers looking to improve their processes and reduce their costs often need the pros and cons up front. And logically so, because changing manufacturing methods is a big step. But, if done right, it can increase efficiency and reduce costs.
For starters, closed die forging is not as precise as some engineers think it is. The freedom to produce net or near-net shapes is minimal, which leads to secondary operations to fix limitations of the closed die forging process. Processes like machining or deburring take up valuable time and decrease profit margins.
Designers have always recognized powder metal as a cost-effective metal-forming process, however, its limited mechanical property performance still leaves them wary of switching to PM. This assumption has been a barrier keeping designers from using PM over traditionally forged components.
For some components, the limitations of conventional PM are very real. Transmission gears and connecting rods are an example. Customers buy cars with the expectation that they’ll run for 250K miles, and PM probably isn’t the best process to provide this. The development of the powder forging process ultimately allowed the con rod to become a PM part, and it has since become the manufacturing process of choice for producers of these components.
Much like PM forging advanced the manufacturing of automotive connecting rods, we’re poised for these unique alloys and ultra high-temp sintering to revolutionize traditional wrought steel applications.
New materials and processes can offer alloying specifically designed to improve hardness and wear resistance while possessing mechanical strength and ductility that is unavailable with conventional PM materials. These new levels of performance offer forge-like properties along with the inherent shape-making capabilities characteristic of PM, resulting in reduced cost.
How to Know Your Part Is Ideal for PM
Consider each project on its own to determine if PM is the right choice. An important factor when it comes down to traditional forging vs. powder metallurgy is shape, minus the significant machining often required with a forged part.
PM allows you to produce complex geometries that would be too expensive to manufacture with closed die forging due to the increased machining requirements. With PM, there are no secondary operations--press, sinter, and done.
There are still a number of forged components in the automotive industry being used today that can be transferred over to this new, exciting PM revolution.
What Are the Steps for Moving to PM?
The first step is to discuss your performance and tolerance needs. Talking with a PM supplier about your design, budget, lead time, production, and delivery needs will sort out what process is best for your part.
To learn more about the capabilities of powder metallurgy, check out our free guide!
In this post we talked a lot about part shape and density, but another benefit of PM is the increased magnetic properties! Keep an eye out for a follow-up blog post about increasing magnetic performance!