Galling Testing

[modey3]

Hello,

I have a question for the tribologists on the board. Is the pin-on-disk test appropriate for testing the galling resistance of different surface treatments? My feeling is no because when you are looking materials with different hardnesses like iron and aluminum, plastic yielding of the aluminum will become a problem. If the 0.5 dia ball is iron, the aluminum will be ploughed at even l lbs loads. If the 0.5 dia ball is aluminum, the aluminum will be sheared away onto the iron surface at even the lightest loads because the normal force and tangential force have a combined effect on the plastic yielding at the tip. Using that setup it would be very difficult to determine a galling threshold. Also, the contact area will change with loading/sliding distance.

I think a flat-on-flat test (such as the ASTM test) should be the most effective at determining the galling threshold, but I would like to hear the opinions of other on this board. Thanks

modey3

[Simon Kim]

First of all, I am not native speaker.

So please understand my broken english.

Pin on Disc test is useful for understanding of Galling properties.

At first you should to consider for edge effect and load carrying capacity.

Pin on disc makes contact area.

So you can predict for pressure of each materials after to compare each modulus of materials.

And then you can decide for the steps of contact stress for test, of course same pressure to materials.

That is first step for prediction of load carrying capacity.

However the result is not satisfactive sometimes, because of edge effect.

Sharp edge makes severe wear track on the disc, so researcher fall into confusion frequently.

He could not compare to exactly.

You have to prevent the edge effect by chamfer or roudness for edge of pin.

I wish your sucessful result!

Simon

[HVoilF]

The Falex Block on Ring test is much better in my opinion for tribological investigation , friction coefficient between pair of materials,wear test ,galling and material transfer consideration. We do use in Venezuela for galling investigation in the repair of big screw pump with Stellite 6 (screws)and carbon steel or stainless steel(casing) mating materials.
Please find information in http://www.falex.com
Regards

(06-16-2010 08:51 PM)modey3 Wrote:  Hello,

I have a question for the tribologists on the board. Is the pin-on-disk test appropriate for testing the galling resistance of different surface treatments? My feeling is no because when you are looking materials with different hardnesses like iron and aluminum, plastic yielding of the aluminum will become a problem. If the 0.5 dia ball is iron, the aluminum will be ploughed at even l lbs loads. If the 0.5 dia ball is aluminum, the aluminum will be sheared away onto the iron surface at even the lightest loads because the normal force and tangential force have a combined effect on the plastic yielding at the tip. Using that setup it would be very difficult to determine a galling threshold. Also, the contact area will change with loading/sliding distance.

I think a flat-on-flat test (such as the ASTM test) should be the most effective at determining the galling threshold, but I would like to hear the opinions of other on this board. Thanks

modey3