Powder metals 1

[dicer]

Just curious, what kind of strengths and notch sensitivity powder metal steels have? There seem to be alot of automotive parts made of this nowadays. Is it a desirable material or just a cost effective manufacturing technique?

 

[CoryPad]

Cost effective manufacturing technique only

 

[btrueblood]

Well...I agree in general that p/m steels will be less fatigue tolerant and lower in strength than their forged counterparts. But, there are types of composite metal materials that can only be made by powder sintering. Dicer, if you want a decent publication that gives a lot of material data for standard P/M materials, see the standards listed here:

http://www.mpif.org/Pubs/stand.asp?linkid=81#pm_parts

 

[unclesyd]

We have polymer gear pumps made from CPM, Crucible Partical Metallurgy, steel that are performing a well as the wrought materials. If I remember correctly they are D2 and M4 for normal use and 10V on high wear polymers.

We also use some powder metal cutting tools with no problems. There is also a lot blades for cutting polymer and fabric made from various alloys.

 

[CoryPad]

No argument about composites, tool steels, and cermets being excellent PM materials. However, these are a far cry from the stuff being used in automotive applications that [blue]dicer[/blue] mentioned.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[NickE]

Yes, however as those of us in automotive know. The cost/price point required forces us to manufacture parts that meet the minimums in many areas.

IE: price....

Just enough to do the job, and at the lowest cost is what we are required to do...

P/M parts are utilized effectively IMHO, when they can be.



Nick
I love materials science!

 

[plasgears]

When you see PM conn rods, then you know PM has arrived. After sintering, they can be air quenched or oil quenched. High end PM products have been heat treated like other steels.

In gear work we oil quenched after sintering, which gave us the toughness we needed to get thru durability testing. The oil helped lube the gears, too.

 

[coatingengineer]

Hi.

Unless I'm missing something, P/M are a far cry from cheap. When you're comparing costs of steel, for example, be sure to include the expense of heat treat. That way, your comparison for resistance to wear, anyway, is more 'apples-to-apples'.

However, even when you factor in heat treat with steel, P/M metals, especially high speed steels, are comparatively more.

Advantages of P/M can come from their grain structure. By increasing alloy content, wear can be measurably improved without compromising toughness.

Hope that helped. Anyway, if you'd like information about surface treatments, like hardening, just see:

<a target="_new" href="

http://www.industrialcoatingsworld.com/Wear-Resistant-Coatings/Hardening.html">Hardening</a>

Good luck!




William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[CoryPad]

PM con rods are forged, which eliminates the porosity inherent in the PM process. That is the only reason PM can be used for con rods. The only advantage PM offers for con rods is the elimination of some machining steps, and hence, a lower cost.

PM for gears in only for light load applications, and again, the advantage is lower machining costs.

William Gunnar is correct that PM materials are expensive - very expensive. The final part cost may be lower due to lower manufacturing costs (like machining). He mentioned wear - PM is used for valve seats made from high alloy materials that have low formability, so the sintering route provides a way to make the part that isn't possible with conventional forming techniques.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[EdStainless]

In many parts the finishing (machining) costs are the major factor. PM tooling and powder aren't cheap, but if you are making a lot of parts it can be very efficient.
I have even converted low volume parts to PM because of machining costs. You have to modify the designs to allow for lower flexure, impact and fatigue strengths, but that is what we do.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[dbooker630]

Having spent a dozen years in the con rod forging world in the 90's, I saw first hand how PM replaced hot rolled bar, with the exception of diesel, marine, and hot rods.

 

[plasgears]

My company avoided machined gears, and we always had justification for PM gears/oil quench in our production quantities.

Another process we introduced in gears was fine blanking, which is a precise blanking process. They were very durable. The blanked gears had the characterisitic flow shape on the side opposite the plunge tool. The reduced section of gear teeth was not objectionable. Strength is needed at the base of the tooth.

One war story: We were getting reduced gear strength, and when we started digging, we found that 2d shift mfg was induction HT and setting the gears aside for quenching as a group!

 

[Robertmet]

Crucible's CPM steels can hardly be called PM in the normal sense !Even the European steels of similar making don't fit the definition even though they are referred to as powder metal. PM covers a wide range depending on density ,alloy HT, even carburizing. From filters to close to wrought properties.Remington always specialized in high density [98-99 % theoretical] which required a double compacting and sintering.
PM has been replaced in many applications by MIM [metal injection molding] .
Like any good engineering a look at the whole picture will decide which material should be used.