The effect of workpiece material and its microstructure on tool wear in metal cutting
Doktorsavhandling, 2019

The aim of the present work is to promote the basic understanding of how the workpiece material and its microstructure affect the tool wear during metal cutting. To isolate the effect of the workpiece material, the tool material (uncoated cemented carbide) was kept constant while the workpiece was varied. The studied workpiece materials were a tool steel, two superalloys, a casehardening steel, and two workpieces of an austenitic stainless steel obtained from different suppliers. After controlled turning tests, the workpiece microstructures and the resulting tool wear was studied, primarily by scanning electron microscopy together with energy-dispersive X-ray spectroscopy and the electron backscatter diffraction technique. The results show that the thermo-mechanical and microstructural properties of the different workpieces result in distinct microscopic features on the worn tool surfaces. The responsible wear mechanisms were identified by assessing the chemical and physical properties of the microstructural constituents in the workpieces. Due to its large amounts of carbides, machining the tool steel was primarily associated with abrasive tool wear. The corresponding wear features on
the tungsten carbide grains were dominated by grooves, micro-fragmentation, and plastic deformation. Similarly, abrasion played a major role when machining the superalloys. Differences in the amount of carbides and inclusions triggered varying degrees of abrasion which affected the overall flank wear when cutting the two investigated superalloys. Flank wear resulting from machining the case-hardening steel is suggested to be due to dissolution combined with mild abrasion. In contrast, the stainless steel workpieces did not contain significant amounts of hard phases which led to mainly dissolution-induced flank wear. The worn tool surfaces were characterized by smooth tungsten carbide grains without micro-fragmentation or plastic
deformation. For the two stainless steel workpieces, the non-metallic inclusions and their ability to form stable layers on the tool surfaces controlled the overall flank wear. If present, a stable inclusion layer provides protection of the underlying tool material against dissolution. Knowledge of the active tool wear mechanisms and their underlying reasons can be used as input for physicsbased wear modelling approaches and allows to identify the role of microstructural variations in workpieces. In that way, the cutting process can be optimized to become more reliable, efficient, and sustainable.

Scanning electron microscopy


Cutting tool


Cemented carbide



Virtual Development Laboratory (VDL), Chalmers Tvärgata 4C, Gothenburg
Opponent: Professor Mikael Olsson, Dalarna University, Falun, Sweden


Philipp Hoier

Chalmers, Industri- och materialvetenskap, Material och tillverkning

P. Hoier, K.B. Surreddi, U. Klement; Tool wear by dissolution during machining of Alloy 718 and Waspaloy: A comparative study using diffusion couples

A. Malakizadi, P. Hoier, U. Klement, P. Krajnik; A critical assessment of tool wear mechanisms when machining alloys with distinctive thermo-mechanical and microstructural properties

In our everyday life we are frequently using different types of mechanical systems like automobiles,
home appliances, or airplanes. Each system usually contains many individual components that have to
work together properly so that the mechanical system as a whole functions. A modern aircraft engine,
for example, contains about 18000 individual components. During manufacturing of most of the
components, different metal cutting operations are used to cut the material (also called workpiece) into
the desired shape. Obviously, the whole engine can only work safely and reliably if every single
component has the exact right shape and dimension. Small deviations due to problems during the
cutting processes can cause catastrophic failures during the service life of the aircraft engine.

One problem that can arise during metal cutting operations is excessive wear of the tools that are used
to cut the workpiece. In such a case, the component that is cut can be damaged and has to be scrapped
since it cannot be applied for its purpose. This problem can be compared to cutting vegetables with a
knife (your cutting tool) in your kitchen at home: After long cutting time and maybe depending on
what types of vegetables you cut, the edge of your cutting tool can wear and get blunt. Instead of
cutting precise slices of for example tomatoes, you will rather squish the tomato and get “damaged”
slices with intolerable dimensions and properties.

In order to avoid this problem during manufacturing of mechanical components, it is therefore
important to know or predict when the cutting tool is too blunt to cut the workpiece precise enough.
This is however difficult, because it is not well understood how the different constituents of the
workpiece affect the wear of cutting tools. It is further complicated by the fact that workpieces can
vary depending on their type and the producer. Similarly, the characteristics of a tomato (for example
size and amount of hard seeds) can vary depending on what kind of tomatoes are used and where they
were grown.

This thesis aims at increasing the fundamental understand of how the workpiece material and
variations in its microstructure affect the wear of the tools used to cut it. This was achieved by
controlled cutting tests during which the amount of tool wear was measured and compared when
cutting different workpieces. Furthermore, the workpieces and worn cutting tools were studied at the
microscopic scale to identify the mechanisms responsible for the wear. The gained knowledge can help
to optimize the cutting process as it allows to predict how fast cutting tools wear down and when they
have to be replaced. In that way the risk for having to scrap components can be reduced which is
beneficial from an economical and an environmental standpoint and leads to more sustainable



Bearbetnings-, yt- och fogningsteknik

Metallurgi och metalliska material





Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4608


Chalmers tekniska högskola

Virtual Development Laboratory (VDL), Chalmers Tvärgata 4C, Gothenburg

Opponent: Professor Mikael Olsson, Dalarna University, Falun, Sweden

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