Characterisation and modelling of the wear behaviour of coated cemented carbide tools used for turning a hard to machine steel

• Applicant: Professor Dr.-Ing. Dirk Biermann
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 468249651

The sustainable and economic future orientation of cutting manufacturing processes requires a significant reduction of critical or rare resources such as tungsten and cobalt on the tool side, as well as the energy required for production. In order to achieve this goal for carbide tools without impairing the operating properties, complex high-performance coatings in multilayer design are used so that the wear progress is delayed and thus the tool life is increased. In addition, cooling lubricant (coolant) systems are used, which not only reduce friction but also the temperatures at the carbide tols and thus also improve its wear behaviour. For an efficient design of application-specific tool concepts, e.g. with regard to their tool shape, numerical chip formation simulations have developed into a powerful instrument. In order to also be able to design the coating concepts of carbide tools with the aid of simulation in the future, realistic models of the wear progress are necessary. For the parameterisation and validation of coating-specific wear rate models, knowledge of the thermomechanical load spectrum is of central importance. Due to the limited accessibility, however, the in-situ recording of temperature gradients on the TCT during machining, especially with the use of cooling lubricants, represents a great challenge, which leads to the need for new temperature measurement methods. In order to enable a more precise determination of the relevant temperatures, the previous project succeeded in developing an innovative test rig on which a spatial resolution of 50 µm can be realised during orthogonal turning without coolant with the aid of a ratio pyrometer including collimator. This test rig is to be expanded within the scope of the proposed continuation project in order to also be able to characterise the influence of a cooling lubricant on the temperature field on multilayer-coated carbide tools as well as the resulting tool wear. To this end, it is advisable to implement a sealing air system in the test rig that removes the cooling lubricant between the tool and the measuring device in order to enable temperature measurement in the contact zone. By recording ex-situ measurement data relating to the shape of the cutting edge, a highly accurate description of the initial condition of the HM tool and a monitoring of the wear progress over the entire tool life is achieved. The measurement data obtained is used to calibrate the wear rate models, which enables individual modification depending on the coolant strategy and the coating properties. The chip formation simulations carried out on the basis of these wear rate models are to be validated with the aid of experimental data from the turning tests in order to predict the tool wear.

• DFG Programme: Research Grants