4. Surface integrity

Machining superalloys and titanium alloys is likely to have marked effects on surface integrity, which must be taken into account because of the consequences for part behavior. These effects include surface roughness, sub-layer microstructure and residual stresses. Crack initiation can be linked to the presence of residual stresses caused by poorly controlled or insufficiently controlled machining. It is therefore important to know exactly what effects machining processes, especially those currently under development, have on surface integrity, and to be aware of how these effects evolve when a machining parameter varies even slightly, particularly when it comes to controlling residual stresses.

It has been shown that, when superalloys are turned, increasing cutting speeds, from the conventional range to the high-speed range described above, leads to a decrease...