Tool wear and tool protection in metal cutting: in-process interaction between workpiece, tool, and environment

In an era where 3D printing and AI are at the forefront, turning, milling, and metal cutting might seem like niche research topics from the past. But metal cutting is all around you. If what you have lying on your desk was not machined, then the tools used to create it certainly were. Even 3D-printed or additively manufactured parts must be machined if a good surface quality is needed for an industrial application or to look shiny and nice.

Being bad at machining is very expensive—not only wasting the limited resources available to us on this planet but also most likely putting you out of business. A tool used in an industrial setting to machine metal costs at least 10 euros but can exceed 100 euros. A tool lasts about 15 minutes and can be used one to four times. The tool is not even the most expensive part of the process, as the cost of the operator, machine, workpiece material, and workshop are also a big part of the cost. A tool breakage during machining is even more expensive, as it might require reworking or scrapping a part worth tens of thousands of euros.

One may think that tools are worn only through mechanical wear, but these tools are extremely hard; for example, diamond is the hardest known material. This resistance to mechanical wear makes chemical degradation play an important role. Modeling this chemical wear can save industry resources and reduce lead times in research projects. It is also a scientifically interesting topic, as chemical degradation at high temperatures and high material flow rates is a complex process that appears in many other research fields.

This thesis combines experiments, advanced microscopy, and chemical simulations to study how and why tools wear and how we can limit it. This allows us to combine the right tool material, workpiece, and process to limit tool wear. It also enables us to optimize the machining process so that a protective layer forms on the tool, further limiting wear. This discovery adds a new dimension to a research field that has been studied for over a century within a manufacturing practice spanning thousands of years.