I bought a stainless steel axle and tested how well it performs in a simple Lego hoist.
How much better is it compared to a normal Lego plastic axle? Enjoy!

The axle specs:
Lego Technic compatible
19 Lego-studs long
stainless steel
bought from Brick Machine Shop on BrickLink (obsolete) https://store.bricklink.com/Eezo?itemID=106643711
later it was sold by cncgear on EBay (obsolete) https://www.ebay.com/itm/19-units-long-stainless-steel-axle-X-style-works-with-Lego-Technic-gears/262583950400
as of Jan 2026, steel axles are available from MTP https://metal-technic-parts.com/products/stainless-steel-metal-axle-compatible-with-lego-technic