Double Glow Plasma Research Articles

High-temperature oxidation resistance and wear properties of functionally graded CrHfNbTaTiN high-entropy nitride coating on Ti alloy

High-entropy nitrides have emerged as promising alternatives to traditional protective coatings due to their excellent comprehensive properties. However, there is still a long-standing technical challenge in the design and manufacture of hard and high-temperature stable high-entropy nitride coatings. This study utilized first-principles calculations to evaluate the thermodynamic stability between high-entropy nitrides and corresponding high-entropy metals, as well as titanium alloy substrates, confirming the rationality of the structural design of the functional gradient high-entropy ceramic coating. Subsequently, a double-glow plasma surface alloying technique were conducted to prepare a CrHfNbTaTiN functional gradient high-entropy ceramic coating on titanium alloy, followed by high-temperature cyclic oxidation experiments and high-temperature ball-on-disk wear tests. The research demonstrates that the gradient composition coating exhibits strong interfacial bonding, with an adhesion strength of around 40 N. It maintains excellent oxidation resistance in environments below 700 °C and displays good high-temperature wear resistance. This study contributes to providing insights and guidance for the further development of high-temperature, high-hardness, and wear-resistant materials.

The influence of nitrogen content on the microstructure and properties of W-Ta-Cr-V-N refractory high-entropy nitrides

To enhance the mechanical performance and corrosion resistance of refractory high-entropy alloys (RHEAs) and to identify materials better suited for severe high-temperature and corrosive environments, this study utilized a double glow plasma surface alloying technique to fabricate a W-Ta-Cr-V-N refractory high-entropy nitride coating on a W substrate. The microstructure and phase structure of the samples were characterized using a scanning electron microscope and X-ray diffractometer. The mechanical properties of the samples were evaluated through microhardness testing, while their corrosion performance was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The study investigated the effects of different nitrogen contents on the microstructure, mechanical properties, and corrosion resistance of the BCC-structured W-Ta-Cr-V alloy in the past tense. The study found that the doping of an appropriate amount of nitrogen can lead to the formation of FCC and HCP structured nitrides. As the nitrogen content increases, there is a significant change in the preferred orientation of the coating. When the nitrogen content is 16.6 at.%, the distribution of the nitrides is uneven, resulting in increased surface undulations and roughness. Conversely, when the nitrogen content is elevated to 48.1 at.%, the clustering of surface nitride particles becomes more pronounced, leading to a decrease in the coating density. The thickness of the nitride coatings is around 10 μm, with a slight decrease in thickness as the nitrogen content increases. The hardness of the coatings is significantly superior to that of the W-Ta-Cr-V alloy films, reaching up to 3465 HV0.25 in the highest instance. The introduction of 31.4 at.% nitrogen results in the densest coating, effectively enhancing the corrosion resistance of the refractory high-entropy alloy. Therefore, the doping of an appropriate amount of nitrogen can alter the microstructure of the refractory high-entropy alloy, improve its mechanical properties, and enhance its chemical stability.

Preparation and properties of CrNiWMoCoTi gradient high entropy alloy layer by plasma surface metallurgy

While titanium alloys excel in a number of ways, they have relatively weak wear resistance. To address this problem, this experiment is based on the research foundation of plasma metallurgy and high-entropy alloy (HEA). A continuous and dense CrNiWMoCoTi gradient HEA layer was prepared on the surface of TC4 by using the double glow plasma metallurgy technique, which significantly improves the wear resistance of TC4, and the HEA layer has a high bonding strength with the substrate. By studying the tissue morphology evolution and properties of the HEA layers under different holding times, it was found that all the HEA layers showed a composite reinforcing layer structure of deposited layer + diffused layer, forming an HEA layer with a gradient structure. The experimental results show that the bonding strength between the alloy layer and the matrix at a precisely regulated holding time of 3h, exhibiting a bonding force of about 63.3 N. Further analysis showed that the holding time had little effect on the phase composition of the HEA layer, and the main phases remained stable including fcc, bcc, hcp, AlMoTi2, and Co1.3Ni4.3Mo4.6 phases. With the adjustment of the holding time, the prepared HEA layers showed different degrees of improvement in terms of hardness and wear resistance. Particularly noteworthy is that the HEA layer held for 3 h excels in both properties, reaching 8.7 times the wear resistance and 1.5 times the hardness of the matrix TC4.

Thermodynamic properties, interfacial adhesion energy and tribological properties between MCN (M = Hf, Ta, Cr, Nb) coating and Ti alloy substrates investigated by experiment and first-principles calculations

A series of MCN (M = Hf, Ta, Cr, Nb) coatings were prepared by double glow plasma surface alloying (DGPSA) as protective hard coatings for Ti60 (Ti-5.5Al-4.0Zr-4.0Sn), aiming to solve the problems of low bonding strength between the ceramic coating and the substrate as well as the poor wear resistant of ceramic alloy coatings. First principles calculation was used to study the elastic constant of MC0.5N0.5 solids, thermomechanical parameters and the interfacial adhesive strength of Ti(101)/MCN(220). The calculated results indicated the HfCN solids show excellent mechanical properties, lower thermal expansion coefficient α, lower Gibbbs values and higher values of entropy (S), superior adhesion strength Wad ∼ 5.7 J/m2. The high-temperature tribological performance tests show that the HfCN and TaCN coatings exhibited better wear resistance compared with the CrCN and NbCN coatings at 500 °C -700 °C. The wear rate of HfCN coatings at 500 °C and 700 °C is about 2 times and 5 times lower than that of CrCN, which is in accordance with the HfCN coating’s excellent thermal stability and high interfacial bonding strength with the Ti substrate. The adhesion wear mechanism of all coatings gradually intensified with increasing temperature.

Structural, mechanical, and oxidation resistance properties of double glow plasma Ta[sbnd]W alloys

To enhance the performance of surface coatings on weaponry, TaW alloy layers with various W contents (7, 11.5, 13, 14, 14.5 and 16 at. %) were prepared on the surface of a PCrNi3MoVA gun steel substrate using double-glow plasma surface metallurgy technology. Mechanical properties, friction wear, and oxidation resistance were studied using scratch, hardness, and tribometer testers. The mechanical properties, interfacial properties, and effects on the oxidation performance of the gun steel substrate of the TaW alloy layer were calculated using first principles. The results indicated that the surface and cross-sectional microstructures of the TaW alloy layers were dense and free from obvious defects. With increasing W content, the thickness, hardness, and adhesive strength of the TaW alloy layer increased, and the coefficient of friction and wear rate decreased. The results of the calculations indicate that an increase in the W content enhances the elastic modulus of the TaW alloy and improves its brittleness, strength, and hardness. Doping with Ta and W atoms can increase the vacancy formation energy of Fe atoms in the Fe supercell, the adsorption energy of O atoms on the surface of Fe(110), and the diffusion barrier of O atoms in the Fe supercell and on the Fe(110) surface. Interdoping of Ta, W and Fe atoms at the Fe(110)/Ta-W(110) interface improved the bonding strength and stability of the interface, and the FeTa and FeW chemical bonds formed at the Fe(110)/Ta-W(110) interface ensured stable bonding at the interface. The incorporation of W into the TaW alloy layer enhanced both the mechanical and frictional properties of the alloy. It is well established that TaW alloys improve the antioxidant properties of gun steel substrates, thereby enhancing the performance of coatings on weaponry.

Substrate dilution and interface structures of tungsten coating deposited by double-glow plasma surface alloying on stainless steel substrate

W-coating layers with varying thicknesses up to 10 μm were deposited by double-glow plasma surface alloying (DGPSA) on finely polished stainless steel (SS304L) substrates to investigate the influence of the substrate on both the W-coating and interface structures. The examination revealed substrate dilution and the presence of oxide crystallites, predominantly FeWO4 and WO2, at the interface between W and SS304L. These observations correlated with the occurrence of cracking and peeling-off of the W-coating. Both Cr and Ni showed decreased distribution in the interface layer compared to their distribution in the W-coating and SS304L substrate. In comparison, Fe demonstrated a more noticeable compositional gradient, decreasing monotonically from SS304L across the interface to the W-coating. The depth distribution of O indicated that its inclusions were influenced not only by DGPSA deposition but also by post-deposition ion-beam milling. Additionally, the presence of spherical particles directly on the substrate's surface provided evidence for surface alloying reactions, while the columnar grains within the interface oxide layer were associated with the texture features of the W-coating, as confirmed by X-ray diffraction and pole-figure measurements. These findings offer valuable insights into the surface alloying process facilitated by DGPSA and its potential for developing W-coatings tailored for plasma-facing applications.

Performance Enhancement of Ti/IrO2-Ta2O5 Anode through Introduction of Tantalum-Titanium Interlayer via Double-Glow Plasma Surface Alloying Technology.

Ti/IrO2-Ta2O5 electrodes are extensively utilized in the electrochemical industries such as copper foil production, cathodic protection, and wastewater treatment. However, their performance degrades rapidly under high current densities and severe oxygen evolution conditions. To address this issue, we have developed a composite anode of Ti/Ta-Ti/IrO2-Ta2O5 with a Ta-Ti alloy interlayer deposited on a Ti substrate by double-glow plasma surface alloying, and the IrO2-Ta2O5 surface coating prepared by the traditional thermal decomposition method. This investigation indicates that the electrode with Ta-Ti alloy interlayer reduces the agglomerates of precipitated IrO2 nanoparticles and refines the grain size of IrO2, thereby increasing the number of active sites and enhancing the electrocatalytic activity. Accelerated lifetime tests demonstrate that the Ti/Ta-Ti/IrO2-Ta2O5 electrode exhibits a much higher stability than the Ti/IrO2-Ta2O5 electrode. The significant improvement in electrochemical stability is attributed to the Ta-Ti interlayer, which offers high corrosion resistance and effective protection for the titanium substrate.

Microstructure, wear behaviour and laser ablation behaviour of double glow plasma alloyed Ta[sbnd]W coating

TaW alloy is considered a crucial candidate for barrel protective coatings due to its high melting point, excellent high-temperature performance, and ablative resistance. In this study, TaW coating was deposited on the surface of PCrNi3MoVA gun steel by double glow plasma alloying (DGPA) technique. The morphology, phase structure, wear property, and laser ablation behaviour of the TaW deposited coating was studied and analyzed by means of scanning electron microscope (SEM), energy dispersive spectroscopy detector (EDS), X-ray diffractometer (XRD), ball-on-disk friction test, and laser pulse heating experiment. The results showed that the coating was dense and metallurgically bonded to the substrate. The coating was primarily composed of the α-Ta phase, and W was solidly dissolved in the Ta to form a mutual solution with solid-solution strengthening effect. The wear mechanisms of TaW coating were adhesive wear and oxidative wear. During the laser pulse heating (LPH) process, the transition region, center region, and splash region appeared successively in the ablation area of the coating. After 10 s of ablation, only a region with a diameter of 0.1 mm was penetrated, highlighting the effective protective role of the TaW infiltrated layer on the substrate.

Study on the structure, growth pattern and corrosion behavior of CoCrFeNiAl high entropy alloy coatings - base on hollow cathode effect

The surface of TC18 titanium alloy was coated with a CoCrFeNiAl HEA coating using double-glow plasma surface metallurgy. The structure, phase, and growth mode of the coating were investigated, along with its electrochemical corrosion behavior. The prepared HEA coating, under the influence of the hollow cathode effect and non-equilibrium diffusion, exhibits a composite structure consisting of a deposited layer and an interdiffused layer. It demonstrates robust metallurgical bonding with the substrate, and it exhibits a hardness of 12.66 GPa and an elastic modulus of 158.52 GPa, along with exceptional hardness and high elastic modulus. The primary phase of the coating consists of an FCC solid solution, with a minor presence of Ni3Al and Al8Cr5 phases. TEM results demonstrate that hollow cathode enhanced sputtering effectively refines the grain structure on the substrate surface. The high entropy alloy coating, characterized by a significant abundance of nanocrystalline and amorphous structures, is obtained under the bombardment of high-energy particles. Gradually increasing from the interface to the deposited layer, there is an augmentation in the content of nanocrystals. The transition from the substrate to the sedimentary layer comprises three distinct regions: a surface fine crystal region, a nanocrystalline structure region, and a nanocrystalline and amorphous precipitated phase-rich region. In 3.5 wt% NaCl solution, the electrochemical corrosion rate of the coating is 1.36 × 10−1 μm·year−1, which is about ten times lower than that of the substrate. Moreover, pre-soaking forms a stable oxide film on the coating's surface, effectively preventing corrosion and demonstrating its remarkable corrosion resistance.

High-temperature oxidation behavior of double glow plasma Cr-Y alloyed layers on Ti2AlNb alloy

A Cr-Y alloyed layer was synthesized on the surface of Ti2AlNb by double glow plasma surface alloying technique. The morphology, phase composition and oxidation behaviors at 750 °C, 800 °C, and 850 °C of Cr-Y alloyed layers were systematically investigated. The results illustrated that Cr-Y alloyed layer was approximately 10 μm thick, which the morphology of alloyed layer was uniform and compact, with a flat and uniform interface to the matrix. Oxidation kinetics for the Cr-Y alloyed layer approximately followed the parabolic law, with an oxidation weight gain significantly lower than that of Ti2AlNb. The predominant oxides of Cr-Y layer were CrNbO4, Cr2O3, and Y2O3, which effectively hindered oxygen diffusion into the substrate.

Wear-resistant ZrN/Ti functionally graded coating prepared on TA18 alloy by double glow plasma alloying

Despite being an excellent structural material, α-Ti alloy is with low shear deformation resistance, resulting in susceptibility to friction damage during service, and limits its further application. A wear-resistant ZrN/Ti functionally graded coating (FGC) was prepared on TA18 alloy by double glow plasma alloying technique in this paper. The morphology, phase structure, mechanical properties and wear behavior of ZrN/Ti FGCs were studied and analyzed. The results proved that a gradient structure formed in the coating: the topmost layer was ZrN ceramic phase, in the transition layer were ZrN, TiN, and Ti2N phases, and in the inner layer was α-Ti phase. The coating was dense and metallurgically bonded with the substrate. It exhibited better load bearing capacity and fracture toughness. Upon conclusion of wear tests under different loads, only slight damage was observed on the coating. The main wear form of the coating was delamination wear, and the ZrN layer on the topmost surface was not worn through. More specifically, the Zr pre-diffusion treatment was used to increase the content of ZrN in the transition layer, reducing the unfavorable Ti nitride phase formed. Therefore, the stress concentration caused by the difference in elastic modulus between the different phases was relieved. Thus, ZrN/Ti FGC with continuous properties and good wear resistance was successfully synthesized.

Dependence of the M choice on the properties of Hf(M)SiCN (M = Nb, Ta, Ti, Zr) ceramic coatings: ab-initio and experimental study

The HfMSiCN coatings (M = Nb, Ta, Ti, Zr) are researched using ab-initio theoretical method and double glow plasma surface alloying. The aim is to enhance the high temperature stability and wear resistance of these coatings, alongside optimizing mechanical and thermodynamic properties. Firstly, the calculated mechanical properties for Hf0.5M0.5CN correlate with those experimental measurement for HfMSiCN. Secondly, the thermodynamic parameters exhibit that the Hf0.5Zr0.5CN has the lowest thermal expansion coefficient and higher bulk modulus at high-temperatures. Moreover, the wear rate of HfZrSiCN at 500 ℃ is less than 60% of its wear rate at 300 ℃. The superior wear resistance of HfZrSiCN coating is attributed to a friction-induced composite layer including a dense amorphous nanocomposite surface layer and a nano-friction glaze layer supported by nanograins.

Combining laser surface texturing and double glow plasma surface chromizing to improve tribological performance of Ti6Al4V alloy

Ti6Al4V (TC4) alloy has been widely applied in the military, industrial, chemical, and medical fields due to their excellent thermal stability, corrosion resistance, and biocompatibility. However, titanium alloys are notorious for their poor tribological properties, such as their high friction coefficients and low surface bearing capacities. To tackle this problem, combination of laser surface texturing (LST) and double glow plasma chromizing was conducted to improve the wear resistance of TC4. LST was first conducted to produce uniform dimples with a diameter of 300 μm and gradient density of 11 % on the Ti6Al4V substrate. A chromizing coating (Cr-coating) was subsequently deposited on the surfaces of the textured and raw Ti6Al4V alloy by double glow plasma surface alloying (DGPSA). A continuous and compact Cr-coating with a thickness of about 55 μm was formed on TC4 after being maintained at a temperature of 850 °C, and the coating was mainly composed of a solid solution and intermetallic compounds of Cr2Ti phases. The surface hardness after alloying was two times higher than that of the TC4 substrate. Comparative assessments on the wear resistance of the Cr-coatings with and without LST treatment and the TC4 alloy were carried out using a ball-on-disk wear tester. The results showed that the mass loss and specific wear rate of the duplex-treated sample were 1.54 mg and 7.14 × 10−4 mm3·N−1·m−1. The mass loss and specific wear rate of the TC4 were 4.32 mg and 1.62 × 10−3 mm3·N−1·m−1. The specific wear rates of the four tested samples were in the following order: the duplex-treated TC4 < textured TC4 < chromized TC4 < polished TC4. The coating obtained by LST-double glow plasma chromizing duplex treatment exhibited an outstanding durability and the best mechanical performance. Thus, this approach be used for the protection of Ti6Al4V surface in engineering components and medical instruments.

High temperature oxidation behaviors of Al/Cr composite coating on Ti2AlNb alloy

The Al/Cr coatings were deposited on Ti2AlNb alloy by magnetron sputtering and double glow plasma alloying technology to improve the oxidation resistance. The morphology of the protective coating was investigated by scanning electron microcopy and the phase composition of the coating was analyzed using x-ray diffraction. The results suggested that the protective coating with multilayer structure was dense and homogeneous. The formation of Cr inner diffusion layer was beneficial to the bonding strength between the coating and substrate, which was attributable to the double glow technology. The oxidation behaviors of Al/Cr coating were investigated by the isothermal oxidation tests for 100 h at 700 °C, 800 °C and 900 °C, respectively. The results indicated that the protective coating showed a lower oxidation rate. At 700 °C, the Al2O3 oxidation products were formed on the surface of coating at high temperature, which were dense and homogeneous against oxygen diffusion. With the increase of oxidation temperature, the external diffusion of Cr element reacted with oxygen to form Cr2O3, which provided the further protection. As for 900 °C, the volatile CrO3 was formed by the reaction of the external diffusion of Cr and Cr2O3, and the oxidation products Al2O3 and Cr2O3 continued to provide protection for Ti2AlNb alloy.

Microstructure and high-temperature oxidation behavior of Al2O3/Cr composite coating on Inconel 718 alloy

In this paper, Al2O3/Cr composite coatings were prepared on the surface of Inconel 718 alloy by cathodic liquid plasma electrolytic deposition (CLPED) and double-glow plasma surface alloying (DGPSA) processes. The microstructure and high-temperature oxidation behavior of Al2O3/Cr composite coating were investigated. The results showed that the Al2O3 interlayer surface was fully covered with Cr coating. The interface between the Al2O3 layer and the Cr metal layer presents a mechanical interlock effect, which can absorb the deformation caused by thermal expansion, thereby reducing the adverse effects of thermal stress. The surface roughness of the Al2O3 coatings decreased after depositing Cr coating. The oxidation weight gain of the Al2O3/Cr composite coatings were significantly lower than that of the substrate, indicating that the Al2O3/Cr composite coatings improved the high-temperature oxidation resistance of Inconel 718 alloy. The oxidation weight gain of the Al2O3/Cr composite coatings at different frequencies were similar, while the Al2O3/Cr composite coating at 400 Hz was lowest. During the high-temperature oxidation process, the Al2O3 interlayer can effectively inhibit the external diffusion of Ni, Fe and other elements in the matrix, which helps to prevent the cracking of the outer oxide film, thereby reducing the oxidation rate.

Effect of C/N incorporation on structural and crystallographic properties of TaNbZr coatings deposited by double-glow plasma surface alloying on Ti-alloy substrate

The relatively low corrosion and wear resistance of Ti-alloy hinders full application of its meritorious low density-to-strength ratio. Here, we studied TaNbZr coatings by double-glow plasma surface alloying (DGPSA), with and without C- or N-incorporation, on TA15 substrate to enhance its tribological properties. The C-incorporation was introduced by adding a graphite target, which decreased the glow discharge on the Ta/Nb/Zr targets and thus reduced the deposition rate by ∼55 %. In comparison, the N-incorporation was introduced by feeding N2, partly replacing the Ar working gas flow, which reduced the sputtering yield of the metal targets that in turn reduced the deposition rate by ∼60 %. Hole and hill-in-hole structures have been observed on TaNbZrC with the size and density much higher than those on TaNbZr and TaNbZrN, which was attributed to undesired graphite particles ejected from the target and deposited directly onto the growing surface of the substrate. The localized ejection induced by the graphite particles upon the substrate-associated glow plasma gave rise to the hole and hill-in-hole structures. The C- and N-incorporation modified the surface alloying reactions, leading to different microstructure and smoothness on the surface, compositional changes of the ‘buffer’ layer at the coating/substrate interface, and varied crystallographic texturing of the coatings. Nanoindentation measurements at the cross-section across the coating/substrate interface provide evidence for the enhanced hardness, not only at the coatings but also at the near-interface regions of the substrate. These observations, together with bonding strength and tribology tests at elevated temperatures, shed new light on developing protective coatings on Ti-alloy by DGPSA.

Isothermal oxidation behavior of W-based alloy coatings doped with Ta, Cr, Ti, V

Tungsten-based multi-alloy coatings with the addition of Ta, Cr, Ti, and V were prepared by double glow plasma surface alloying (DGPSA) technology. The alloyed specimens showed bulges and pits on the surface with an island growth mechanism. The coating exhibits a single BCC phase. The hardness shows an increasing trend with the increase of alloyed elements. The maximum hardness value of WTaCrTiV is 1748 HV100g. The oxidation behavior of coatings at 800 °C was investigated, with emphasis on the effect of elemental doping on the antioxidant properties. With the addition of Ta, Cr, Ti, and V elements, the antioxidant properties of multi-alloy coatings were effectively improved compared the tungsten matrix. The WTaCrTi coating shows the optimum antioxidant properties with a dense Cr2O3 layer. As the number of elements in multi-alloy increases, the mixing entropy increases, leading to a decrease in the Gibbs free energy, which results in a more stable alloy.

A series of plasma innovation technologies by the double glow discharge phenomenon

In order to break the limitation of plasma nitriding technology, which can only be applied to a few non-metallic gaseous elements, the “double glow discharge phenomenon” was defined and then the “double glow plasma surface metallurgy technology” was invented. This double glow plasma surface metallurgy technology can use any element of the Periodic Table for surface alloying of metallic materials. Countless surface alloys with special physical and chemical properties have been produced on the surfaces of conductive materials. By using the double glow discharge phenomenon, a series of new double glow plasma technologies have been developed to apply to surface metallurgy, graphene technology, brazing, sintering, arc plasma surface alloying, nanotechnology, cleaning, carburizing without hydrogen, and so on. This article briefly introduces the basic principles, functions, and characteristics of each technology. The application prospects and development directions of plasma in metallic materials and the machinery manufacturing industry will also be discussed.

Structure and performance of iridium electrocatalysts for hydrogen evolution reaction obtained by electrodeposition and double glow plasma: A comparative study

Iridium (Ir), with low overpotential and excellent stability, is a promising catalyst for the hydrogen evolution reaction (HER) in alkaline electrolyte. Structure and HER performance of Ir electrocatalysts fabricated by electrodeposition (ED) and double glow plasma (DGP) were investigated. ED Ir nano electrocatalyst with rough surface was not completely covered and consisted of a mixture of nanocrystalline and amorphous. Homogeneous and dense DGP Ir electrocatalyst with micro-size was composed of many coarse particles. After ablation, the Ir grains coarsened, and many holes were formed. Boasting a large electroactive surface area and high electrical conductivity, ED Ir electrocatalysts exhibited a superior electrocatalytic activity in 1.0 M KOH solution, requiring only 0.044 V overpotential to obtain a current density of 10 mA·cm−2, with a low Tafel slope of 34 mV·dec-1 and a high exchange current density of 0.669 mA·cm−2, compared with DGP Ir electrocatalysts with and without high-temperature treatment. The electrocatalytic activities of the electrocatalysts were in order of ED Ir > DGP Ir > ablation Ir electrocatalysts.

Characterization of a CrN/Cr gradient coating deposited on carbon steel and synergistic erosion-corrosion behavior in liquid‒solid flow impingement

Erosion-corrosion resistance is a critical factor in the service life extension of metallic structural materials in front of complex flow and solid impingement. To improve the erosion-corrosion resistance, a CrN/Cr gradient coating was fabricated on carbon steel by the double glow plasma alloying technique. The CrN/Cr gradient coating mainly consists of the CrN phase and (Fe, Cr) metal phase. Debye rings from the X-ray pattern illustrated that the coating was under a compressive stress of 868 MPa. Residual stress and fine toughness of the gradient structure enhanced its adhesion strength, endowing it with the potential to accommodate strains caused by external forces. The potentiodynamic polarization test illustrated that the addition of solid particles and the increase in flow velocity severely weakened the protective ability. The mass loss rate results illustrated that the synergistic effect made the greatest contribution to the erosion-corrosion damage of the CrN/Cr gradient coating, while its proportion increased as the flow velocity increased. Compared to the substrate, the gradient structure of the coating facilitated interruption of the sharp interfaces, thereby reducing the deformation mismatch and enhancing the damage tolerance of the coating.