Knowledge of wear paves the way for next-generation rock drilling inserts

Jens Hardell, Professor at Luleå University of Technology and project manager for ReRoD. Photo cred: Daniel Holmgren, Cre8photo

The research project Recycled Rock Drill Tools for Sustainable and Circular Mining (ReRoD) has investigated methods for measuring and evaluating wear in cemented carbides, with the aim of increasing the use of recycled material in rock drilling inserts. The results show that recycled cemented carbide can perform at a level comparable to material produced from virgin raw materials, an important step towards a more resource-efficient and circular mining industry.

The ReRoD project aimed to increase the use of recycled cemented carbide in tools for rock drilling by evaluating tribological test methods for measuring wear under different operating conditions. The background is that the cemented carbide inserts used in drill bits contain both tungsten and cobalt, two critical raw materials, making recycling particularly important.

Recycling can make use of the substantial remaining cemented carbide material often left in the inserts when the drill no longer performs satisfactorily. This can help reduce dependence on primary critical raw materials. However, a key requirement is that inserts containing recycled raw material must deliver the same premium performance as cemented carbide produced from virgin raw material. To understand performance at a fundamental level, increased knowledge of wear is essential for enabling further material development.

“The main objective of the project was to evaluate different laboratory tests and build fundamental knowledge about the ability of these test methods to reproduce relevant conditions between cemented carbide and different minerals, as well as to generate comparative wear data and descriptions of wear mechanisms for cemented carbide,” says Jens Hardell, Professor at Luleå University of Technology and project manager for ReRoD.

Several challenges arose during the project. The tribological tests proved to be more complex than expected, particularly at high temperatures. This was mainly due to variations in the material properties of the mineral samples, for example granite, which had a significant impact on the results from the wear tests.

The collaboration within the consortium worked very well. The two academic partners, Luleå University of Technology and KTH Royal Institute of Technology, brought complementary expertise that contributed to a successful collaboration. The industrial partner Sandvik Mining and Construction Tools AB also showed strong commitment by contributing personnel resources, materials and several experimental investigations.

The project’s most important results concern new wear data and identified wear mechanisms for cemented carbide in contact with granite at temperatures up to 800°C.

“This data has not been published before, and we identified both interesting trends and challenges related to the test setup and the materials at these high temperatures. The comparison shows comparable performance for cemented carbide produced with recycled raw material and cemented carbide produced from virgin raw material, which strengthens the possibilities to increase the share of recycled material. In addition, the mapping of different test methods for measuring wear in cemented carbide rock drills has laid the foundation for developing the next generation of test methods,” says Jens Hardell.

The project also led to some unexpected findings. Among other things, the wear of the cemented carbide varied significantly depending on the characteristics of the granite samples. The researchers also observed that the wear of the granite increased markedly at higher temperatures, which had not been expected.

Following the completion of the project, parts of the results will be published in scientific journals. A substantial share of the knowledge and results will also form the basis for a new application for funding for a larger and more comprehensive research project. The planned follow-on project will develop new test methods to further increase knowledge of wear in cemented carbide. This knowledge will support the continued development of cemented carbide containing recycled material and enable the next generation of rock drilling inserts.