Here you'll find free 4K damagemasks, wearmasks und scratchmasks. Put them into the alpha channel of your material setup to simulate
realistic damages on the surface. Since all maps here are greyscale only they work also quite well as displacement source.
Scratchmasks are key for photorealistic renderings and enhance your work extremely! Have a look at this short (under 2 minutes!) YouTube tutorial from Maxon how to apply these images into your
material channels: Scretchmasks & worn out edges