New Development of Surface Finishing Processes for Tungsten Carbides

Updated: Jun 2


MAY 11, 2022


GPAINNOVA has achieved significant technological advances in surface finishing for cemented carbides, also known as hard metal (WC-Co), by means of the dry electropolishing technology.


In 2021 a new process based on dry electropolishing was developed for hard metal. The patent pending process is part of the DryLyte® Technology and supposes the solution to leaching of cobalt binder and other side effects of the technology. The new electrolyte and process was patented by Marc Sarsanedas, Guiomar Riu and Joan Josep Roa.


Two studies have been accepted to be published in Procedia CIRP (ISSN 2212-8271). Both are related to surface integrity at the submicrometric length scale after being polished by the mentioned technology for WC-Co. These researches have been developed by GPAINNOVA, the Department of Materials Science and Engineering of the Polytechnic University of Catalonia (UPC) and the KLA Group.


The studies confirm that dry electropolishing technology removes roughness of WC-Co substantially without a leaching effect of the metallic cobalt (Co) binder.



Surface integrity of the new dry electropolishing technology for WC-Co-cemented carbides


This study focuses on WC-Co parts treated with the dry electropolishing technology (DryLyte®). This solution allows to obtain corrosion-free surfaces with an average roughness below 9 nm as shown in Figure 1. The main goal behind this research is to investigate the surface integrity in terms of mechanical properties, mainly hardness, at the submicrometric length scale as a function of the polishing time. The quality of the surface has been evaluated by using advanced characterization techniques and the mechanical response obtained through the Nanoindentation technique treated by using a statistical methodology. To sum up, a close correlation is observed between the surface integrity and the polishing time.

Figure 1. Cross-section micrograph showing no leaching effect (left hand side) and FESEM micrograph of WC-CO grade (right hand side) after being polished using the DryLyte® Technology for 30 minutes.



Conclusions


  • The DryLyte® Technology allows to polish WC-Co, reducing roughness and removing post-processing defects induced during the grinding process.

  • The polished specimens do not show any leaching effect on the metallic Co binder.

  • Nanoindentation tests show a clear correlation between microstructure and mechanical properties.



Small-scale mechanical response at intermediate/high temperature of 3D printed WC-Co


In this work, a systematic study has been carefully implemented to dry-electropolished 3D-printed WC-Co specimen with complex. The research has subsequently evaluated the mechanical integrity for each constitutive phase (either with different nature “WC and/or Co phases” or crystallography WC orientation) as a function of the testing temperature.



Conclusions


  • Hardness is a temperature-dependent property.

  • The WC particles present an anisotropic behavior in terms of hardness for temperatures below 500 ºC.