# Influence of Micro-Textures on Cutting Insert Heat Dissipation
## 3 Experimental Study
### Heat Transfer Rate Results and Discussion  
The micro-textures effectiveness in promoting heat extraction is evaluated by comparing the heat transfer rate of the cutting inserts with and without micro-textures. The study involved four consecutive tests on three samples of each of the four insert models presented in Figure 6, corresponding to a total of forty-eight experimental measurements. All the tests were conducted for the input power level of 400 W, being measured the inlet T1 and outlet T2 temperatures and the mass flow rate of water after reaching the steady-state regime, see Figure 7. The respective heat transfer rate is evaluated according to Equation (1), by considering the mass flow rate of water, the temperature difference between inlet and outlet, and the constant specific heat of 4187 J/kg.K.  
Table 4 presents the average and the standard deviation values of the temperatures T1 and T2, the respective temperature difference \(\Delta\)T, the mass flow rate of water, and the heat transfer rate results per sample and insert model. Indeed, an increase in the heat transfer rate is observed with groove depth, corresponding to 0.92%, 2.58%, and 3.77% for Grid depth 1, Grid depth 2, and Grid depth 3, respectively. Similar values among the three samples for the same insert model are found. However, this is also followed by the increase in the respective standard deviation, which is associated with the higher dispersion of results within the same insert model. A possible explanation for this is the difference in the depth of the grooves between the samples. As already mentioned, these are created using laser ablation on green compacts. The amount of material removed will depend on the distance from the laser focal point to the compact green surface. The height of these compacts may vary slightly between samples and within the sample due to their manufacturing process and, therefore, grooves with different depths may be produced. This deduction results from the observation of the surface topology by scanning electron microscopy (SEM), which is shown in Figure 8 for the three different depths. The images reveal a non-uniform distribution of the depth of the grooves along the grid, which degrades with grooves depth. Furthermore, these compacts are post-dewaxed and sintered, which also contributes to cutting inserts geometric distortions [40]. These distortions were identified on the lateral faces of the cutting inserts, due to the increase of thermal contact resistance with heat sources. The problem was overcome by placing a thin layer of aluminum between the two elements.  
Figure 8: Images of surface topology by scanning electron microscopy.  
These results were only possible to obtain due to strict control of temperatures and the input power during the experimental tests. The measurement procedure allowed us to identify variations of less than 1% in the heat transfer rate.  
These experimental results agree with the ones presented by other authors, that the inclusion of micro-textures leads to a decrease in the cutting insert temperature [16; 20]. Furthermore, we can say that the contribution of microtextures to heat extraction is small compared to other tribological effects, such as the reduction of the contact area and the friction coefficient, which agrees with the findings presented by other authors [17; 21; 32].