# Comprehensive Study of the Mechanical and Tribological Properties of NiCr-Al Detonation Coatings
## 2 Materials and Methods
It was found that GC NiCr-Al-based coatings can be produced by varying the filling volume of the detonation barrel with explosive gas during detonation spraying [41,42]. For comparison purposes, an HC NiCr-Al coating was also produced. The technological parameters used for the deposition of NiCr-Al coatings are presented in Table 1.  
The phase composition of the coatings was analyzed using an X'Pert PRO X-ray diffractometer (PANalytical, Amsterdam, The Netherlands). X-ray phase analysis was performed using CuK\(\alpha\) radiation under the following conditions: voltage U = 40 kV; current I = 30 mA; exposure time 1 s; step size 0.02\({}^{\circ}\); diffraction angle 20 10-90\({}^{\circ}\). The analysis of the diffractograms was carried out using the HighScore software (version 3.0e) with the PDF2 database. The porosity of the coatings was evaluated using an Olympus BX53M metallographic microscope. Image analysis was performed on the micrographs to determine the pore area fraction. The surface microstructure and morphology of the cross-section of the coatings were examined using scanning electron microscopy (SEM) with the SEM3200 (CIQTEK Co., Ltd., Hefei, China) device and energy-dispersive X-ray analysis (EDX) equipment from Bruker Corporation, Billerica, MA, USA). The adhesion strength of the coating was tested according to ISO 14916 [46] using the Elcometer 510 device (Eldometer Instruments, Manchester, UK) (Figure 4). The samples were bonded to the counter surface using the Epidian 53 cold-curing epoxy adhesive, which has a theoretical strength of 70 MPa. During the test, pins with a diameter of 10 mm and a loading rate of 0.4 MPa/s were used. Microhardness measurements were performed using a Metolab 502 tester (Metolab, Russia) in accordance with GOST HCU 6507-1 [47]. A static load of 100 g was applied to the diamond indenter for 10 s, and five independent indentations were made on each sample surface for statistical reliability. The hardness and elastic modulus along the cross-section of the coatings were measured using the NanoScan-4 DCompact device (Troitsk, Russia). The measurement of hardness and elasticity modulus along the cross-section of the coatings is performed in accordance with GOST 8.748-2011 standard [48] using the NanoScan device and NanoScan Viewer software (version 200). The loading and unloading rates were maintained at 10 mN/s, and the dwell time at maximum load was set to 5 s. \begin{table}
\begin{tabular}{c c c c c} \hline
**Coating** & **O\({}_{2}\)/C\({}_{2}\)H\({}_{2}\)** & **Spraying** & **Barrel Filling** & **Number of** \\
**Structure** & **O\({}_{2}\)/C\({}_{2}\)H\({}_{2}\)** & **Distance, mm** & **Volume, \%** & **Shots** \\ \hline Homogeneous & 1.856 & 150 & 50 & 40 \\ \hline  & & & 50 & 10 \\ Gradient & 1.856 & 150 & 40 & 10 \\  & & & 30 & 10 \\  & & & 25 & 10 \\ \hline \end{tabular}
\end{table} 
Table 1: Deposition parameters for HC and GC NiCr-Al produced by the detonation spraying method. Tribological tests in dry sliding conditions were conducted at ambient (room) temperature using the \"Ball-on-disk\" method on a TRB\({}^{3}\) tribometer ([PERSON], Buchs, Switzerland) in accordance with ASTM G 99 standard [49] (Figure 5a). A 3.0 mm diameter ball made of SH15 steel was used as the counterbody. The tests were conducted at a load of 10 N and a linear velocity of 0.03 m/s. The wear track radius was 4 mm and the total length of friction test was 100 m. For the tribological tests at ambient (room) temperature, three independent measurements were performed. Tribological testing of the coatings at high temperature using the \"Ball-on-disk\" configuration was performed on T-21 model ribotesters at the Department of Machine Design and Tribotechnology, AGH University of Krakow, in accordance with ISO 20808:2016 standard [50] (Figure 5b). The tribological testing schematic is shown in Figure 5b.