Additive manufacturing (AM) has recently been accorded considerable interest by manufacturers. Many manufacturing industries, amongst others in the aerospace sector, are already using AM parts or are investing in such manufacturing methods. Important material properties, such as microstructures, residual stress, and surface topography, can be affected by AM processes. In addition, a subtractive manufacturing (SM) process, such as machining, is required for finishing certain parts when accurate tolerances are required. This finish machining will subsequently affect the surface integrity and topography of the material. In this research work, we focused on the surface integrity of Ti-6Al-4V parts manufactured using three different types of AM and finished using an SM step. The aim of this study was to gain an understanding on how each process affects the resulting surface integrity of the material. It was found that each AM process affects the materials’ properties differently and that clear differences exist compared to a reference material manufactured using conventional methods. The newly generated surface was investigated after the SM step and each combination of AM/SM resulted in differences in surface integrity. It was found that different AM processes result in different microstructures which in turn affect surface integrity after the SM process.

Due to increasing demand in manufacturing industries, process optimization has become a major area of focus for researchers. This research optimizes the cryogenic machining of aerospace titanium alloy Ti-6Al-4V for industrial applications by studying the effect of varying the nozzle position using two parameters: the nozzle’s separation distance from the tool–chip interface and its inclination angle with respect to the tool rake face. A finite element model (FEM) and computational fluid dynamics (CFD) model are used to simulate the cryogenic impingement of cryogenic carbon dioxide on the tool–workpiece geometry. Experiments are conducted to evaluate cutting forces, tool wear, and surface roughness of the workpiece, and the results are related to the CFD and FEM analyses. The nozzle location is shown to have a significant impact on the cutting temperatures and forces, reducing them by up to 45% and 46%, respectively, while the dominant parameter affecting the results is shown to be the separation distance. Cryogenic machining is shown to decrease adhesion-diffusion wear as well as macroscopic brittle chipping of the cutting insert compared to dry turning, while the workpiece surface roughness is found to decrease by 44% in the case of cryogenic machining.

Innovative textured alumina coatings have been engineered to boost the performance of cutting tools. Different workpiece materials affect the wear inside the CVD textured alumina coating differently on the crater and flank side of the tools. How the balance in wear changes between the crater and flank side of the tool inside the alumina is not fully understood. Furthermore, any changes in steel elements in the workpiece can affect this balance differently. In this work, the wear of alumina coating has been studied after turning different workpiece materials (low alloy steel with and without Ca, ball bearing steel and stainless steel). The worn surfaces of the inserts were studied and their features related to the different materials. It was found that after machining under similar conditions, each workpiece material leaves a different signature, or worn surface, with unique features in the alumina coating layer. The transition between the sliding to the sticking region was studied in order to help understand the relation to wear when machining different workpiece materials. SEM and topography characteristics were identified on worn surfaces of the coated tools. The resulting worn volume and surface characteristics were related to different wear mechanisms acting on the rake and flank sides of the tool. This work studies the shift in balance between crater and flank wear by identifying different wear mechanisms acting inside the same alumina coating layer when machining different grades of steel. Such work can be a good resource for FEM wear modeling, where good simulation models must take into consideration the physics lying behind the wear types acting on each side of the tool.