I did some tests with scenes to show some simple techniques for improving rendering results.
In first project i use texture for bumping. With this you`ll get very small surface details. And you can use the same texture in color channel for additional variations.
By using different noises in bump I created small surface structure and welding seam. Materials are mixed with curvative.
Of course you can use a more complex setups and blends with additional textures packs. But this is a learning project for my classes and i cann`t distribute others people textures, that`s why my goal is to show some very basic setups.