HC anodized aluminum + steel wear. With picture ! 1

[EdDantes]

Hello,


I need to know if this setup will last a relatively small amount of cycles.


In the picture, you will see where a steel button [latch] locks into a mating part.


Typically, the mating part, is made of steel. We will say a heat treated carbon steel. Rc 20-30 (give or take). In this case, aluminum was chosen as a substitute for weight and corrosion advantages.


It appears in this photo that the steel button [latch] is locking into an anodized aluminum piece.


This will work but I have been told it will not stand up over time. For obvious reasons, like hardness of the different materials.


6061-T6 : 95 [Brinell]
4130 : 302 [Brinell]


We will use those 2 materials for argument's sake. The aluminum is correct. I am not 100% sure on the steel used.


Ok, so here is the break-down.


Steel button [latch] that is around 3 times harder than 6061-T6.


6061-T6 interface part. Hard Coat Anodized. Brings Rc up to 60-70.


Hinge pin made of stainless steel.


What problems are we looking at here ?

Accelerated galvanic corrosion ?
Accelerated wear ?
Others ?


How do we eliminate these problems ?

Link to picture :

http://img87.imageshack.us/my.php?image=afterel8.jpg

 

[unclesyd]

Does the Al part flip 180 and the pin hold it place or does the Al move across the end of the steel pin?

Normally unlubricated/lubricated anodized Al will wear steel. Even though non-anodized Al is used for bearings it has to be lubricated to function.

 

[EdDantes]

The AL interface part, where the steel locks, is static.


Just imagine a door knob type lock. The AL part would be the part that goes in the door frame [non moving]. The steel part would be the angled/reciprocating locking part that goes into the AL part.


The steel part is spring loaded so that it depresses when it comes into contact with the AL piece. It will lock into the AL piece.


So you are saying that the HC anodizing would stick just fine and not wear away ?

This is important, not for appearance, but for the wearing of the aluminum and galvanic weakening of the substrate.

The parts need a good solid lock [steel into aluminum]. I just wondering if, over time, the anodizing would wear and cause a loose fit due to tolerances.


I hope this makes sense ?

 

[coatingengineer]

Hi, Ed.

Unless you're operating in some inert atmosphere, or under vacuum, wear rarely exists without corrosion. That's just the way it is.

In fact, whether your environment is "wet" or "dry", there are at least a dozen related mechanisms for failure. So, most likely, your wear debris includes corrosion products.

Is your hard anodize intact? Or is contact stress, plastic deformation so high as to cause your hard anodize fracture? (If that happens you'll definitely stimulate localized corrosion between (steel or atainless steel) with your aluminum.

Identify your wear mechanism. Find the mode of failure. This will really help you select the right materials and surface treatments for your program.

Here, this will help you get up to speed, quickly:

<a TARGET="_new" href="

http://www.industrialcoatingsworld.com/Wear-Resistant-Coatings/index.html">Wear

Resistant Coatings</a>

Good luck!


William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[unclesyd]

what is the environment the part operates in?

Can you apply a dry film lubricant to the AL anodized part?
This can be short time test to see if a lubricant would help the situation

How many cycles are you talking about?

Is it to make the Al part out of a different material?

Can you look at the two pieces under magnification to see if the Al is picking up steel debris and moving them around?

A lot depends on the amount of force the Al has to overcome when the two come together. It should help to minimize the force use to lock the two parts together.

He is an excellant paper on wear by Peter Min that might help you understand the mechanisms of wear.

http://www.solorb.com/dat-heads/digests/V4.100/D100