I have conducted the cylinder on cylinder fretting wear tests at various loads (i.e. 30-60 N). The wear scar and COF decreases with increasing load.
Suppose you push a fridge across the floor and box of match the heavier one will have more friction but it will also depend on the texture of structure or two surfaces
Check the formation of tribolayer on the surface of tribopair. The tribolayer can act as a solid lubricating layer.
The sliding (kinetic) friction are expressed as three laws: Amontons' First Law, Amontons' Second Law, Coulomb's Law of Friction.
However, in real life not all the laws are valid. For instance: dry friction of rubber on concrete - Amontons' Second Law does not work.
I think you can look towards two directions:
1. Surface roughness. High load smooths out asperities, and that can change the friction and wear mechanisms (this is defined by the material you use).
2. Special features of fretting process. Change in load causes a change in the size of the slip zone, so the contact conditions can change non monotonically (in slip region).
In occasions higher loads causes rupture of the material and forms debris. Depending on the type of material, this entrapped debris could act as small bearings, reduce the coefficient of friction and reduce wear with higher loads.
It should be analyzed according to specific materials. Some materials have self-lubricating properties. When the load is increased, physical and chemical reactions will occur on the friction surface to generate solid lubrication film and reduce the friction coefficient.
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