From Particles to High-Performance Cutting Tools – The Optimization of Industry Scale Powder Processing (aw)

Background

High-performance cemented carbide tools for cutting and milling of steel and other metal alloys are very important for the industrial production of modern high-precision engineering components, for example engine and machinery parts used in the automotive and aerospace industry. Micron-sized tungsten carbide and cobalt powders are the main base materials for the production of cemented carbide tools. The powders are commonly suspended in a liquid for mixing and homogenization and the resulting particle slurry is spray-dried to obtain free-flowing powder granules. Shaping and densification of a cemented carbide tool is achieved by dry-pressing the free-flowing powder and sintering the powder compact at high temperatures to full density.

Experience from industrial production tells us that particle properties such as particle morphology and particle size distribution have a strong impact on slurry processing, pressing performance and sintering behavior, all of which are crucial for the quality and reliability of the final cemented carbide product. For example, the compaction pressures required to press spray-dried powders into a desired shape can change significantly depending on the characteristics of both the spray-dried granules and the WC grains. However, quantitative correlations between powder characteristics, powder processing parameters and pressing performance are needed that can reliably link pressing and sintering performance to measurable particle properties. In particular, the ball milling necessary to mix and homogenize particle slurries needs to be investigated with respect to its effect on particle and slurry properties. Similarly, the effect of slurry properties on the microstructure of spray-dried granules and the relation between granule microstructure and pressing performance is of great interest for the optimization of powder processing in industrial production.


Project

Scope of the project
The project aimes at improving our understanding of the milling, spray-drying and dry-pressing operations based on correlations between WC, Co particle properties and pressing and sintering performance. As a result of a systematic study including different WC, Co raw materials and milling treatments we want to be able to use measurable particle properties (e.g. particle size distributions before and after milling) and slurry properties (e.g. viscosity) to control or even predict the outcome of dry-pressing and sintering operations. The relation between particle properties and compaction pressure as well as sintering shrinkage is of particular interest in this context. In addition, novel slurry formulations containing organic additives can provide a promising approach for the production of spray-dried powders with taylor-made properties and will be compared to standard formulations. Experimental work will be concerned mainly with particle sizing based on laser light scattering methods, rheology measurements carried out with a rotational rheometer and microstructure evaluation using scanning electron microscopy. An attempt to develop a simple method for granule density measurement based on image analysis of microscopy images will be made. Additional data that can be included in the thesis will be obtained via external partners (e.g. specific surface area measurements) and the processing laboratory at Seco Tools (e.g. compaction pressure and dimensional changes upon sintering of standard geometries). The tasks included in this work will be performed in collaboration with both R&D and production units at Seco Tools.

The company
Seco Tools is one of the largest producers of cemented carbide cutting and milling tools worldwide. All subsidiaries and production facilities around the world together account for about 4000 employees. Seco Tools AB with ca 1500 employees and the company’s main office is located in Fagersta, Sweden, ca 60 km northwest of Västerås. The advertised project is well suited for