Corrosion Resistance of Nanostructured Cemented Carbides with Alternative FeNi and FeNiCo Binders.

Nanostructured cemented carbides with Co binders have shown excellent mechanical properties in various applications. Nevertheless, their corrosion resistance has shown to be insufficient in different corrosive environments, leading to premature tool failure. In this study, WC-based cemented carbide samples with different binders were produced using 9 wt% of FeNi or FeNiCo with the addition of Cr3C2 and NbC as the grain growth inhibitors. The samples were investigated using electrochemical corrosion techniques: the open circuit potential Ecorr, the linear polarization resistance (LPR), the Tafel extrapolation method, and the electrochemical impedance spectroscopy (EIS) at room temperature in the solution of 3.5% NaCl. Microstructure characterization, surface texture analysis, and instrumented indentation were conducted to investigate the influence of corrosion on the micro-mechanical properties and the surface characteristics of the samples before and after corrosion. The obtained results indicate a strong binder chemical composition's effect on the consolidated materials' corrosive behavior. Compared to the conventional WC-Co systems, a significantly improved corrosion resistance was observed for both alternative binder systems. The study shows that the samples with the FeNi binder are superior to those with the FeNiCo binder since they were almost unaffected when exposed to the acidic medium.

Distribution of coolant during drilling with open type internally cooled medical steel drill.

INTRODUCTION: Internally cooled bone drills with an open system, conduct coolant directly to the point of contact of cutting surface of the drill and the bone and lower the temperature at the drilling site. During bone drilling with internally cooled drills of open type, there is a possibility that coolant enters the intramedullary canal and has an adverse effect on intramedullary pressure. In this research, the intramedullary distribution of the coolant during and after drilling was analyzed. MATERIALS AND METHODS: Specially constructed open type internally cooled medical steel drills were used. Experimental studies were conducted on the porcine femoral bone diaphysis. Coolant (saline) was mixed with water-soluble contrast agent and x-ray images of the distribution of coolant during and after drilling were taken with different regimes of drilling (drill rotational speed from 1300 rpm to 5000 rpm, and coolant flow rate from 0,6 l/min to 1,35 l/min). RESULTS: An x-ray images showed that coolant did not spread from the borehole and has not spread intramedullary with any combination of coolant flow and drill rotation regimes. CONCLUSION: Coolant does not disperse into the intramedullary canal outside of the borehole in given flow ranges (0,6-1,35 l/min) and drill rotational speed regimes (1300-5000 rpm). Open type internally cooled can safely be used for bone drilling.

Experimental and finite element analysis of surgical drill bits with and without irrigation channel - A case study approach.

The aim of this study was to perform a finite element and experimental comparative analysis of the mechanical characteristics of surgical drill bits used in bone and joint surgery applications with and without an irrigation channel. Internally cooled drills are very efficient in maintaining the drilling temperature below the critical level. However, a cooling channel could potentially have a negative influence on the drill structure, particularly in the flutes zone. A commercially available type of surgical drill bit without irrigation channel and a modified variant with the built-in channel were simultaneously loaded with torque, axial and bending forces with magnitudes similar to and higher than those utilized in clinical practice. When loaded under the same conditions, both types of drills showed very similar mechanical properties in the sense of the average von Mises stress in chosen sections and the deflections after plastic deformation. The highest stress was observed in the bending zone which was located at the beginning of the flutes section of the drill. All analysed drills suffered only from plastic deformation without any breakage despite the fact that they were loaded with forces higher than those expected in normal operational conditions.