# Prediction of Cutting Parameters of HVOF-Sprayed Stellite 6
## 3 Experimental Work
### Residual Stress Measurement for Verification and Comparison of the Results  
Residual stress measurement was performed in the laboratory of the Department of Machining and Manufacturing on a Proto iXRD diffractometer. The sample areas were cleaned after the milling operations. Due to the measured material, a Cr K\(\alpha\) lamp was used. The samples were placed on an automated adjustable table under the measuring head, the measured areas being parallel to the axis of the diffractometer arm. An X-ray collimator with a 2 mm diameter was used to focus the X-rays during the measurement; the exposure time for the tilting of the measuring head was set to 2 s for optimal diffraction peak intensity. Residual stress was measured on the samples by triaxial analysis on an X-ray  
Figure 5: Machining of Stellite 6.  
Figure 6: Measurement of surface roughness.  
Polynomial regression equations for individual materials are given by (42) to (44):  
\[R_{mpA} =3.94879+0.29167\cdot E_{xpNO} \tag{42}\] \[R_{mpB} =5.01964+0.37076\cdot E_{xpNO}\] (43) \[R_{mpC} =9.49936+0.70157\cdot E_{xpNO} \tag{44}\]  
In addition to the parameters defined above, the following parameters are represented in the physically discrete equations: \(f_{0}\) [mm]--feed at the neutral plane, \(v_{c0}\) [m\(\cdot\)min\({}^{-1}\)]--the speed at the neutral plane; \(a_{p0}\) [mm]--depth of cut at the neutral plane, \(Ra_{0}\) [m]--surface roughness at the neutral plane, \(k_{mes}\) [-]--constant according to the \(Ra\) measurement conditions, vibration etc.  
The parameters for the neutral plane are determined by the relationships (45) to (48):  
\[v_{c0}=\frac{(Ra_{0}+4.65991)}{0.06193} \tag{45}\]  
\[a_{p0}=2\cdot\left(-0.405+0.005\cdot v_{popt}\right) \tag{46}\]  
\[D_{gr0}=\frac{10^{3}\cdot Ra_{0}}{\sqrt{E_{mat}}} \tag{47}\]  
\[f_{0}=\frac{D_{gr0}}{8.51} \tag{48}\]  
The new parameter \(Y_{retS}\) in the above relationships is the deviation of the tool track from the set plane. The \(Y_{retS}\) parameter is also used to calculate the tangential shear stress in the cut \(\sigma_{t}\) (49) and also to determine the deviation \(\delta\) from the set plane:  
\[\sigma_{t}=2\cdot 10^{-3}\cdot E_{mat}\cdot\frac{Y_{ret}}{Y_{ret0}} \tag{49}\]  
where \(Y_{retS0}\) is the deviation of the tool track from the set cutting plane at the neutral depth \(a_{p0}\), while it has a constant value \(Y_{retS0}=1\) mm.  
This deviation is given by (50):  
\[\delta=arctg\left(\frac{Y_{ret}}{h}\right)\cdot\frac{180}{\pi} \tag{50}\]  
and at the neutral plane of the cut is given by (51):  
\[\delta_{0}=arctg\left(\frac{Y_{ret0}}{a_{p0}}\right)\cdot\frac{180}{\pi} \tag{51}\]  
The present equation \(Ra_{mp}=\) f (\(R_{mp}\), \(E_{xpNO}\)) is sufficient to satisfy this requirement. If we know the integral quantity of roughness, we can derive other main topographical functions according to the previously derived equations of equilibrium [21; 22; 23; 24; 25; 26] and we can calculate with them further. Further, the \(Y_{ret}\) value preferably serves to calculate the tangential forces and the stress for the adhesion control. The structure and texture of the surface after machining is sufficiently discretely expressed by equations (\(Ra\), \(Y_{ret}\), \(a_{p}\)) = f (\(R_{mp}\), \(E_{xpNO}\)). For sufficiently discretely expressed grain size \(D_{gr}\) of the coating material was derived [21; 22; 23; 24; 25; 26] the equation of Equation (35) for different materials. Discrete distribution of particle size distribution by discrete cutting parameters can be determined by \(D_{gr}\) = f (\(R_{mp}\), \(E_{xpNO}\)).