# Prediction of Cutting Parameters of HVOF-Sprayed Stellite 6
## 3 Experimental Work
### Materials and Experimental Procedures  
Stellite 6 as the Co-Cr-W alloy is predominantly utilized in industry. A layer of the Stellite 6 sprayed on the surface can be applied using various technologies, for example, plasma transfer arc (PTA), inert tungsten gas (TIG) welding, thermal spraying or laser coating. Tables 1-3 show the chemical composition of the Stellite 6 spray, its basic mechanical properties, the nominal values of the stress, as well as the nominal values of hardness in hot conditions. The specified mean composition values of Stellite 6, which were obtained from the Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM/EDX) measurement [27], the density of the test material being 8.44 g\(\cdot\)cm\({}^{-3}\), can be found in Table 1.  
The table does not present the temperature changes of nominal stress values \(E_{mat}\), \(Rp_{0.2}\), \(Rm\) of the core of the examined material as dominant within the framework of adequate changes of its surface. However, in general, under certain conditions (especially statically indeterminate structures), the effect of heating on deformation may exceed the effect of mechanical (tensile and compressive) forces for the core material. For the surface of the examined material, the change in surface hardness is observed as dominant within temperature changes (Table 3). The presented experiments applied the spraying technology HP/HVOF JP500 implemented at the Research and Testing Institute in Pilsen, Ltd. The parameters of spraying can be found in Table 4. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & **Co** & **Cr** & **W** & **Mo** & **Si** & **Mn** & **Ni** & **Fe** & **C** \\ \hline \% Wit & 59.68 & 28.34 & 4.1 & 1.69 & 1.23 & 0.27 & 1.66 & 0.79 & 2.24 \\ \hline \end{tabular}
\end{table} 
Table 1: Chemical composition values of Stellite 6 determined by EDX measurement and verified as identical to nominal composition (mass %). \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & **20 \({}^{\circ}\)C** & **100 \({}^{\circ}\)C** & **200 \({}^{\circ}\)C** & **300 \({}^{\circ}\)C** & **400 \({}^{\circ}\)C** & **500 \({}^{\circ}\)C** & **600 \({}^{\circ}\)C** & **700 \({}^{\circ}\)C** & **800 \({}^{\circ}\)C** & **900 \({}^{\circ}\)C** \\ \hline
**HV** & 410 & 390 & 356 & 345 & 334 & 301 & 235 & 155 & 138 & 95 \\ \hline \end{tabular}
\end{table} 
Table 3: The nominal value of hardness of Stellite 6 spray in hot condition. Before spraying with aluminium oxide, the conditions were as follows: grain size 0.8--1 mm (F22); roughness \(Ra=8\) um; Flame Spray Technologies (FST) component 484.074 Stellite 6; alloy based on powder alloy, with a nominal composition of 28% Cr; 5% W; 1.2% C; 1% Si. During spraying, particles of the size 20-53 um atomised by gas were applied. Within the framework of experimental verification, we used cylindrical samples with a diameter of 54.7 mm made of the base material C45, onto which a Stellite 6 was applied by High-Velocity Oxygen Fuel spraying; according to the conditions presented in Table 4, an average layer thickness was 0.55 mm. The length of the machined part of the sample was determined to be 88 mm. The machining was performed using a TUNGALOY RNGN 120400 LX11 43 tool, which was clamped in a MRGNR2525M12 tool holder (Figure 5). The actual experimental verification was performed on the general purpose for centre lathe MASTURN 50/C80 according to the conditions specified in Table 5. \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Value** \\ \hline Oxygen & 996 L min\({}^{-1}\) \\ Fuel & 277 L h\({}^{-1}\) \\ Barrel length & 150 mm \\ Spray distance & 360 mm \\ Traverse speed & 250 mm s\({}^{-1}\) \\ Feed rate & 46 g\(\cdot\)min\({}^{-1}\) \\ Carrier gas & Nitrogen, 6.5 L\(\cdot\)min\({}^{-1}\) \\ Offset & 6 \\ Number of passes & 7 \\ \hline \end{tabular}
\end{table} 
Table 4: Spray parameters.