Klaus Gerschwiler

Advanced machining of titanium- and nickel-based alloys

At present, the majority of tools used for turning titanium- and nickel-based alloys are made of carbide. An exceptionally interesting alternative is the use of PCD, whisker-reinforced cutting ceramic or PCBN tools. Turning nickel-based alloys with whisker-reinforced cutting ceramics is of great interest, mainly for commercial reasons. A change from carbides to PCD for turning operations on titanium-based alloys and to PCBN for nickel-based alloys should invariably be considered if the advantages of using these cutting materials, e.g. higher cutting speeds, shorter process times, longer tool lives or better surface quality outweigh the higher tool costs.

3D Modelling and Simulation of Gun Drilling

The main objective of this paper is the development and validation of a three dimensional thermomechanically coupled finite element model for gun drilling AISI 4150 quenched and tempered steel. The Lagrangian formulation proposed in the FE code DEFORM 3DTM and the constitutive Johnson-Cook material model were utilized to simulate the chip formation and to predict the cutting reaction forces as well as the temperature in gun drilling process using carbide gun drills with two different diameters. During gun drilling simulation, modified gun drill cutting edge rounding and friction law are performed to investigate the effect of tool wear and lubrication on feed force and torque respectively. Experimental gun drilling tests were carried out in steel AISI 4150 for the validation of the developed 3D FE model. The developed and validated 3D FE model can be used for optimizing the cutting process in gun drilling (good surface finish and straightness) taking into account the complex gun drill geometry, cutting conditions, heat transfer and the thermo-mechanical behaviour of the workpiece material.

Performance of γ-Al2O3-Based Coatings and Environmentally Friendly Lubricants in Cutting Operations of Difficult-to-Machine Materials

The machining of difficult-to-cut materials such as nickel-based alloys and austenitic steels are focus in a lot of investigations for a long time. When machining these materials, different effects are overlapping. Approaches to overcome the several problems when machining these materials can be an appropriate coating system for the cutting tool as well as innovative lubricants. Coatings are one of the most common possibilities to improve the cutting performance of tools, notably the tool life as well as the material removal rate. Aluminium oxide coatings made by Physical Vapour Deposition (PVD) technology is a promising coating material for cutting operations. Due to its outstanding characteristics, such as high hardness, high thermal stability and low tendency to adhesion aluminium oxide is a predestined material for the machining of difficult-to-cut materials. In combination with innovative environmental friendly lubricants, the performance of cutting tools is increasing significantly. The objective of this work is to study the wear mechanisms and the cutting performance of aluminium oxide based coated tools in turning, drilling and milling operations.