aluminium pulley

[yusoff]

I am trying to design a pulley made of extruded aluminium using aluminium 6061 T6. we tried to achieve a comparable durability with a cast iron pulley. however we found out after continuous testing for about 800 hours, we noticed a significant wearing on the surface but at the same time the cast iron pulley we had for comparison arent showing any wear sign at all. what could have caused the wear? or we have chosen the wrong material for this purpose. if we have to continue using the material, is there any solution to solve the wear problem? surface treatment etc?

thanks

 

[diamondjim]

Aluminum is a very porous surface
and probably eats the belts.
Possibly a coating to fill in the
pores might improve the life.

 

[EnglishMuffin]

There is probably something in the belts, or on the belts, that is harder than the aluminum. Some "fillers" which are added to rubber and plastics are surprisingly hard. I had an experience recently which brought this home to me - although it is not directly relevant to this case. I was using some 1/8" Armstrong vinyl floor tile as a sacrificial back-up for a thin piece of aluminum that I was machining with a brand new 1/2" HSS milling cutter. Within a distance of about 10 inches the vinyl had worn a 1/16" radius on the end of he cutter!
I assume that these are V-groove pulleys. It is usual to anodize aluminim for this sort of application, but how long that would last I don't know. Hard coat anodizing is about .002" thick and should help - its extremely hard. Its also possible that the free carbon present in a cast iron pulley acts as a lubricant in some way. There are all sorts of proprietary coatings for aluminum which have been developed in recent decades.