Filed under: Top Forging Questions
Like any manufacturing process, powdered metal (PM) has advantages that makes it useful for specific applications. With PM one can produce many small components quickly. In terms of metallurgical properties, forging is still superior. Forgings are used for critical components where part failure could lead to dangerous situations, and PM could not fill this role.
Well, the way forging is superior to powdered metal, the traditional powdered metal process where powder is put into a cavity with a binder, compressed and then subsequently sintered to form a nearly solid part, is that a forging is a solid part. It is 100% dense. Forging is going to have better mechanical properties, better yield and tensile, better elongation, better toughness, better fatigue properties. All of those kinds of things are what you’re going to get out of the forging process that the powdered metal process, simply, cannot produce.
The advantage that powdered metal has, is the ability to produce parts at a much higher rate of speed than forging. Typically, that’s the case. So, if you need a part that doesn’t need that kind of structural integrity and you need a lot of small parts, tens of thousands or hundreds of thousands, powdered metal might be the right way to go. But if you really need a part that is structurally sound, that is going to be a critical component, you really do need a forging. A powdered metal part just isn’t going to cut it.
Now, powdered metal, typically, does have an advantage in that it is much nearer to net shape than a forging. And it may be that it can be used as a powdered metal part with no additional operations to it. That is not always the case, however. Sometimes, they are going to have to be sealed. They’re going to have to be coated so that that porosity that is in that powdered metal part is not been a detriment to the component in its final use. With a forging, you don’t have any of those kind of problems.
So, it’s got a niche. But compared to forging, there is no comparison as far as properties, mechanical properties. You simply are not going to use a powdered metal part as a critical structural component in any kind of an assembly you’re going to produce. That’s where a forging really is going to be a much better part. So, how do forgings and powdered metal parts compare in actual use out in industry, out in the world? Well, you know, there’s actually a combination powdered metal, forging component that is made, that is connecting rods. These connecting rods have been made this way for dozens of years, at this point. And yes, they do start with powdered metal and they make a compact, but it’s still not good enough to be a connecting rod. So, they come back and they forge it.
So, what does that combination actually give them? It gives them some accuracy and speed that you get out of powdered metal. But it gives them that additional strength from the deformation energy of forging. Now, those con rods are still not as strong as a forged, fully forged con rod. But they’re good enough for the particular application. So, again, they’ve almost got it, but they have to add a forging process. So, if you really want the best, it’s a forging.