Tallinna Tehnikaülikool

PhD Project in Mechanical Engineering

Thesis title: Steel-bonded “green” cemented carbides for
applications in metallic materials processing
PhD Programme: Mechanical Engineering
Supervisor: Kristjan Juhani, Senior Research Scientist
Co-supervisor: Fjodor Sergejev, Associate Professor
Offered by: School of Engineering,
Department of Mechanical and Industrial Engineering

Description of the work
WC-Co hardmetals are widely used as cutting tools and wear resistant parts. High price, limited availability and toxicity of cobalt motivates researchers and material engineers to find alternative binder systems for WC cemented carbides.
Therefore the motivation of planned doctoral study stems from: (1) raw materials supply and price and (2) healthcare and environmental safety considerations. Both are considered in Strategic Research Agenda of EuMaT. Substitution of critical raw materials (CRM) and recycling will be essential in the future manufacturing value chain. The proposed doctoral study is related to advanced wear resistant PM materials for a applications in metallic materials processing, in particular “green“ WC-based cemented carbides bonded with Fe alloys.
Co and W in cemented carbides are CRM of the EU. Additional considerations come from the health perspective. In Europe, the REACH programme have classified Co as toxic. A promising substitute for Co has been Ni, but it is also classified as carcinogen. Fe as a prospective substitute in composites has largely been disregarded because of mechanical properties. However, it has advantages over Co and Ni, such as low cost, heat treatment potential, high strength. Shortcomings related to processing could be improved by proper choice of components and preparation techniques.
The results of the study will provide answers to crucial problem in the hard materials industry related to the potential of Co and Ni substitution by “green” (non-toxic) and “abundant” (not consisting CRM-s) Fe-based alloys in WC-based cemented carbides. The main outcomes generated during the study are: (1) advanced “green“ wear and corrosion resistant ceramic-metal composites and (2) powder metallurgy technologies for their production.

Goals of the work
Improving understanding of the structure formation processes during the preparation and hot consolidation (sintering) of starting powders of Fe-alloys bonded WC-based composites (cemented carbides).
Engineering and characterization of Fe-alloys bonded WC-based cemented carbides with structural strength and wear performance comparable with Co-bonded ones in conventional conditions and with better properties in corrosion conditions in a wide range of temperatures.
Development of industrially applicable fabrication technologies (both conventional and additive manufacturing) for production of prototypes and products from developed ceramic-metal composites.

The requirements for the PhD candidate:

  • MA degree in Metallurgy or Materials Engineering with strong conceptual knowledge about Powder Metallurgy, cemented carbides (hardmetals and cermets)
  • Skills and experience in materials microstructural characterisation (optical microscopy, SEM, XRD etc) by use of quantitative methods
  • Materials testing skills are not prerequisite but beneficial as all produced cemented carbides will be tested for characterisation of the materials mechanical properties: strength (TRS, fracture toughness, hardness), wear resistance (erosion, abrasion, adhesion, corrosion) and fatigue. Some industrial testing may be required also.

The doctoral study will be financed from the funds of Professorship of Processing of Metals (PMT).