Composite coatings based on chromium carbide (Cr₃C₂) and nickel–chromium alloys (NiCr) are widely used due to their unique properties, including high heat resistance, wear resistance and corrosion resistance. This article studies the structural–phase and physical–mechanical characteristics of Cr₃C₂-NiCr composite coatings applied by high-velocity oxygen fuel to E110 zirconium alloy. The HVOF method was chosen to create coatings with high adhesion to the substrate and excellent performance properties. Analysis of the microstructure of the cross-section showed the thickness of the modified surface layer from 75 to 110 μm, depending on the processing modes. Energy dispersive X-ray spectral analysis revealed the presence of elements Cr, Ni, C and O in the coating composition. Structural–phase analysis confirmed the formation of coatings with a high concentration of Cr₃C₂ carbide particles and NiCr (nickel–chromium) phases. The resulting composite coatings based on Cr₃C₂-NiCr had a significantly high microhardness, ranging from HV 1190 to HV 1280, and the friction coefficient varied in a significant range from 0.679 to 0.502 depending on the processing conditions. The maximum adhesion strength was 9.19 MPa per square centimeter.

In this work, the influence of spray parameters on the formation of the microstructure, phase composition, and the tribological properties of detonation flame sprayed coatings was studied. It was determined that the chemical composition of Cr₃C₂-NiCr coatings during detonation spraying depends on the degree of filling the barrel with an explosive gas mixture. The degree of filling the barrel with an explosive gas mixture at 73 leads to a decrease in the content of carbide phases, and at 57 filling of the barrel, an increase in carbide phases is observed. It is established that the decrease of the filling degree leads to the increase of hardness and wear resistance of the Cr₃C₂-NiCr coatings since the hardness and wear resistance of the coating material deposited at 57 is higher than at 65 and 73; this is due to the increase in the carbide phase Cr₃C₂. Detonation flame sprayed Cr3C2-NiCr gradient coatings have been developed in this study, which is carried out by varying the spray parameters. It was found that in the gradient coating, Cr₃C₂-NiCr carbide phases gradually increase from the depth to the surface. The obtained gradient coating closer to the substrate consists of the CrNi₃ phase, while the coating surface consists of CrNi₃ and Cr₃C₂ phases.

In this work, the coatings obtained by a combined method, including Cr₃C₂-NiCr coating applied using a multichamber detonation device and subsequent pulse-plasma treatment, were investigated. This paper presents the results of an investigation of the influence of the pulse-plasma treatment (PPT) exposure distance on the structural-phase state of the surface layer of Cr₃C₂-NiCr-based detonation coatings. It was seen that after the PPT melting and alignment of the structural elements of coatings there were no signs of coating destruction from the impact of plasma pulses. It was established that the microstructure of the coatings was a molten metal–ceramic material based on Cr₃C₂-NiCr. It was also found that after pulse-plasma treatment, Cr₂O₃ chromium oxide phases are found on the surface, and the intensity of Cr₃C₂ peaks increased and new Cr₃C₂ reflexes appeared. It was further found that after pulse-plasma treatment the microstructure became more homogeneous, which led to the densification of the Cr₃C₂-NiCr-based detonation coating. It was established that the pulse-plasma treatment (PPT) contributed to increased hardness of the Cr₃C₂-NiCr coating material, from ~13.4 GPa (before PPT) to ~17.6 GPa (after PPT) and wear resistance twice that of the non-treated coating. The abrasive wear resistance and erosion resistance of Cr₃C₂-NiCr coatings were improved after pulse-plasma treatment.

The structural-phase composition and tribological and performance properties of coatings based on an 86WC-10Co-4Cr composition obtained by the HVOF method at varying (150 L/min, 170 L/min, 190 L/min) oxygen flow rates were studied. The results showed that the coefficient of friction of coatings in gear oil remained almost unchanged with the variation in oxygen flow rate. However, microhardness increased significantly with an increasing oxygen flow rate, reaching a maximum at 190 L/min. An increasing oxygen flow rate was also accompanied by an increase in roughness and coating thickness, with a decrease in porosity, particularly notable at 190 L/min. Adhesion strength reached the maximum values for the A2 and A3 coatings under high loads. The phase composition of the coatings included WC, W₂C and CoO phases irrespective of the oxygen flow rate, and their microstructure was characterized by a more homogeneous and dense structure. Thus, this study confirmed that the optimal oxygen flow rate for achieving an improved performance and tribological characteristics of 86WC-10Co-4Cr coatings is 190 L/min.

The article presents the results obtained from experimental studies of Cr₃C₂–NiCr coatings applied, using the detonation-spraying method, on grade 12Kh1MF heat-resistant steel, including those on the effect that the Cr₃C₂–NiCr coating application process technological parameters have on the coating’s structure and properties. In the tests, a detonation gun with a single dosing device was used. Detonation gun spraying is one of the methods for thermally producing a protective layer on the surface, characterized by the fact that it allows hard, wear resistant and dense microstructured coatings to be obtained. Acetylene–oxygen mixture served as combustible gas, which is most frequently used for detonation spraying of powder materials. A nitrogen or air pulse is used for purging the gun barrel after each detonation. This process is repeated several times a second. A high kinetic energy of hot powder particles, as they collide against the substrate, results in that a very dense and strong coating is produced. The obtained coatings have a heterogeneous layered porous structure with undulate location of 60–120 µm-thick structural components with the layered-porous structure. There are no pores or cracks at the substrate-to-coating interface. The profile arithmetic mean deviation R_a is selected as the key roughness measurement parameter. It has been determined that, with the gun barrel volume filled by 64% with explosive mixture, the processed sample surface features a low wear degree. The results from studying the effect that the detonation spraying has on the coating structural-phase composition and tribological properties using the X-ray structural analysis method are given, which have shown that the Cr₃C₂, Cr₇C₃, Cr₃O₆, Cr₂₃C₆, and CrNi₃ phases are produced. The microhardness, roughness, and tribological properties of the obtained coatings have been determined.

This study presents a comparative investigation of the structure, adhesion and corrosion properties of homogeneous and gradient Cr₃C₂-NiCr detonation coatings formed on the surface of 12Kh1MF steel. A Cr₃C₂-NiCr composite powder with a composition of 75/25 and a particle size of 10–45 µm was used to apply the coatings, using a CCDS2000 detonation spraying system. A homogeneous coating was formed at a constant gas mixture filling ratio of 57 per cent, whilst a gradient coating was obtained by sequentially varying the filling ratio from 57 to 64 to 73 per cent, which ensured the formation of layers with different structural and phase states. An investigation of the microstructure and elemental composition revealed a uniform distribution of components in the homogeneous coating and a regular variation in the Cr and Ni content across the thickness of the gradient coating. X-ray phase analysis identified the presence of the Cr₃C₂, Cr₃Ni₂ and CrNi₃ phases. Corrosion resistance was assessed using the potentiodynamic polarization method in a 3.5 per cent Na₂SO₄ solution and through long-term tests in hydrochloric acid mist with the addition of CuCl₂·2H₂O, lasting up to 1000 h. The polarization curves of the gradient coating were shifted towards the region of lower current densities, indicating a slowing down of both anodic and cathodic electrochemical processes. In the tested specimens, visible corrosion was first observed on the homogeneous coating after 456 h, whereas no visible corrosion damage was observed on the gradient coating after 1000 h. Mass loss amounted to 1.14 per cent for the homogeneous coating and 0.17 per cent for the gradient coating. The enhanced corrosion resistance of the gradient coating is due to its denser layered structure and the barrier effect of the interlayer boundaries, which prevent the propagation of through-cracks and the penetration of the aggressive medium to the ‘coating-substrate’ interface. The results obtained demonstrate the potential of forming a Cr₃C₂-NiCr gradient structure to enhance the protective and operational characteristics of detonation coatings.