OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 2 2023 a b Fig. 6. Dependence of the changes in the crystal lattice parameter of the phases of the ZrN/CrN multilayer coating on temperature – a; dependence of the changes in the crystal lattice parameter (Δa) of the phases of the ZrN/CrN multilayer coating on temperature – b for the heating range from 50°C to 550°C, the XRD (β) of the ZrN phase of the multilayer coating will be calculated as: 6 1 6, 99 4, 6065(600 50) 4, 6242 4, 6065 10 ZrN - - - β = = - ⋅ Ê . In the case of the CrN coating component, it can be seen from Fig. 3a that the dependence is not linear but consists of two linear segments. The first segment is 50–400 °C, and for it, the CLTE should be calculated separately. For the linear heating range from 50 °C to 550 °C, the lattice constant (β) of the CrN phase of the multilayer coating will be calculated as: 6 1 8,79 4, 2599(400 5 4, 2468 4 0) , 2599 10 CrN - - - β = = ⋅ - - Ê . In the temperature range from 50 °C to 400 °C, the component of the CrN multilayer coating undergoes compression. The second section, from 400 °C to 600 °C, should also be calculated separately. For this linear heating range, the lattice constant of the CrN phase of the multilayer coating (β) is calculated as: 5 1 4,2849 4,2468 4, 49 4,2468(600 400) 10 CrN - - - ⋅ β = = - Ê . In the temperature range of heating from 400°C to 600°C, the expansion of the component of the CrN multilayer coating occurs, but the CLTE of the CrN component is an order of magnitude higher than that of the ZrN component of the multilayer coating. For clarity, Equation 2 can be represented in graphical form as a dependence of the change in the lattice parameter (Δa) on the temperature of exposure, as shown in Fig. 6b. The tangent of the slope angle in this case is the rate of change in the value of the lattice parameter (nm) per 1 °C during heating. The CLTE value for ZrN phase in the temperature range of 50 °C to 600 °C is positive and equals 3.44×10–5 nm/K, as shown above the red straight line. For the CrN phase of the multilayer coating, in the temperature range of 50 °C to 400 °C, the CLTE value corresponds to a negative value of -5.55×10-5 nm/K. The positive CLTE value is observed in the temperature range of 400 °C to 600 °C, and it equals 1.61×10-4 nm/K for the CrN phase of the multilayer coating.
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