Surface integrity in machined aluminum alloys: Effects of cutting tool coatings and cooling/lubrication

Manufacturing processes significantly influence the type of surface that is being produced. The quality of the surface dictates the functional performance and service-life of engineered components. Residual stresses and surface roughness are some of the important constituents of these manufactured surfaces. Hence, knowledge about factors that cause residual stresses will contribute to a better fundamental understanding of manufacturing process mechanics and improved knowledge-driven manufacturing process planning.;This thesis presents the results of an experimental investigation into the effects of cutting tool coatings and materials, and cutting fluid (CF) application, on residual stresses in machined 7075-T6 and 2024-T351 aluminum alloys measured using the hole-drilling method. Machining is performed with flat faced and grooved (chip breaker) TiN, TiB2 coated carbide tools, and uncoated polycrystalline diamond (PCD) tools in three CF application conditions: dry, minimal quantity lubrication (MQL), and flood conditions. PCD is not a coating but is treated as a thick macro coating for the sake of comparison.;A grooved TiN tool when used to machine 7075-T6 in MQL condition induced the highest near-surface residual stresses; in contrast, when 2024-T351 is machined by the same cutting tool in flood condition, it produced the lowest residual stresses when compared to the respective work material specimens. Thus, it is evident that a specific cutting tool material and/or geometry produce vastly different surface integrity when it is combined with varying coolant/lubricant conditions or when dealing with different work materials.;Therefore, the effect of the interaction between the workpiece, cutting tool, and CF application on residual stress distribution is extremely significant rather than individual effects that are typically reported. The results from this thesis also illustrate some unique tribological challenges encountered in the generation of surfaces and their resulting surface integrity. The results of this thesis have the potential to aid in choosing the cutting tool and CF that are best suited for machining a particular work material. This thesis also throws up several directions for future research on fundamental modeling of the interactions between parameters such as tool coatings and CF application and their significant effects on resulting surface integrity and component life.