Effect of Oxygen Content on Surface and Subsurface Integrity During Turning of Ti–6Al–4V

The load‐bearing capacity and fatigue life of mechanically stressed titanium components are largely determined by surface and subsurface properties such as surface hardness and residual stresses. Titanium alloys have a high chemical affinity for oxygen. However, it is not yet known how the atmospheric oxygen present during cutting interacts with the resulting surface and subsurface properties. This study therefore investigates the influence of oxygen content on the resulting roughness of the workpiece surface, the microhardness of the workpiece surface, and the residual stresses during turning of Ti–6Al–4V as a function of the oxygen content of the ambient atmosphere. An innovative approach is the utilization of a gas mixture of argon and silane, which replaces the ambient air and thus creates an atmosphere that resembles an extremely high vacuum (XHV‐adequate) in terms of oxygen content. The results demonstrate that the oxygen content of the atmosphere does not influence surface roughness. However, the use of the XHV‐adequate atmosphere increases the surface hardness of the machined components by up to 7.8% compared to machining in air. Furthermore, the residual stresses of components manufactured in an XHV‐adequate atmosphere exhibit up to 287 MPa higher compressive residual stresses compared to components manufactured in air.