Cr3C2-NiCr Coatings Research Articles

Impact of hBN Content on the Tribological Behavior and Thermal Diffusivity of HVOF-Sprayed Cr3C2-NiCr Coatings.

Considering the significant health risks posed by hard chrome plating during its application, thermally sprayed Cr3C2-NiCr cermet coatings represent a suitable alternative. Incorporating hexagonal boron nitride (hBN) as a dry lubricant into the feedstock powder can further enhance wear resistance and thermal conductivity, crucial for preventing premature failure caused by inadequate lubrication. In this study, the mass fraction of hBN was varied between 0 and 15 wt.% to assess its influence on the tribological performance of the coatings using pin-on-disk tests. The coating's hardness was measured via the Vickers method, and its cracking tendency at the coating/substrate interface was evaluated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to analyze the microstructure and phase composition, while thermal diffusivity was determined using the laser flash method. The findings revealed that the inclusion of hBN, at concentrations of up to 10 wt.%, leads to an improvement in thermal diffusivity and a reduction in the coefficient of friction. However, exceeding this threshold leads to a decrease in hardness and increased crack formation tendency, highlighting the trade-off between frictional and mechanical properties.

Erosion Wear Behavior of HVAF-Sprayed WC/Cr3C2-Based Cermet and Martensitic Stainless Steel Coatings on AlSi7Mg0.3 Alloy: A Comparative Study

The paper presents a comparative study of the erosion wear resistance of WC-10Co4Cr, Cr3C2-25NiCr and martensitic stainless steel (SS) coatings deposited onto an AlSi7Mg0.3 (Al) alloy substrate by high-velocity air‒fuel (HVAF) spraying. The influence of the abrasive type (quartz sand or granite gravel), erodent attack angle, thickness, and microhardness of the coatings on their and Al substrate’s wear resistance was comprehensively investigated under dry erosion conditions typical for fan blades. The HVAF-spraying process did not affect the Al substrate’s structure, except for when the near-surface layer was 20‒40 μm thick. This was attributed to the formation of a modified Al-Si eutectic with enhanced microhardness and strength in the near-substrate area. Mechanical characterization revealed significantly higher microhardness values for the cermet WC-10Co4Cr (~12 GPa) and Cr3C2-25NiCr (~9 GPa) coatings, while for the SS coating, the value was ~5.7 GPa. Erosion wear tests established that while Cr3C2-25NiCr and SS coatings were more sensitive to abrasive type, the WC-10Co4Cr coating exhibited significantly higher wear resistance, outperforming the alternatives by 2‒17 times under high abrasive intensity. These findings highlight the potential of HVAF-sprayed WC-10Co4Cr coatings for extending the service life of AlSi7Mg0.3-based fan blades exposed to erosion wear at normal temperatures.

Improving hot corrosion behaviour of Cr3C2-25NiCr coatings by reinforcing nano yttria stabilized zirconia at 850 °C

Yttria-Stabilized Zirconia (YSZ)-enhanced Cr3C2-25NiCr coatings were applied to T22 boiler tube steel using the High Velocity Oxy Fuel (HVOF) method. Conventional Ni-20Cr, 5 wt.% YSZ- Cr3C2-25NiCr, and 10 wt.% YSZ- Cr3C2-25NiCr composite coatings were prepared. High-temperature corrosion tests were conducted on both uncoated and coated samples in a Na2SO4-60%V2O5 environment at 850°C under fluctuating thermal conditions. These experiments were carried out in a silicon tube furnace at high temperatures, with each sample subjected to 50 cycles of exposure. Each cycle consisted of 1 hour in the corrosive environment followed by 20 minutes of cooling at room temperature. Corrosion products were analyzed using energy-dispersive x-ray analysis (EDS) and scanning electron microscopy (SEM). The addition of YSZ to the Cr3C2-25NiCr coatings significantly improved corrosion resistance, with the Ni-20Cr, 5 wt.% YSZ-Ni-20Cr, and 10 wt.% Cr3C2-25NiCr coatings reducing overall weight gain by 73.08%, 84.70%, and 89.96%, respectively, compared to uncoated T22 steel.

Microstructures and properties of nano-modified multimodal Cr3C2-NiCr coatings made through laser cladding

Microstructures and properties of nano-modified multimodal Cr3C2-NiCr coatings made through laser cladding

High-temperature tribological properties of NiCr-Cr3C2 cermet coatings in fluoride molten salts

In this work, the NiCr-Cr3C2 coatings with different Cr3C2 contents were prepared via high-speed laser cladding. The relationships between the composition, microstructure, and high-temperature tribological properties in fluoride molten salts were systematically studied. The results suggest that with the increase of Cr3C2 content, the friction coefficient tends to decrease and stabilize, while the wear rate initially decreases and then increases. Especially for the coating with 60 wt% Cr3C2, it exhibits a favorable tribological performance mainly due to the enhanced hardness imparted by Cr3C2, with an average friction coefficient of 0.12 and a wear rate of 2.78 × 10−6 mm3/Nm. However, the coating experiences delamination damage at 70 wt% Cr3C2 content, leading to an increase in wear rate.

Comparison on erosion performance of HVOF sprayed NiCrSiBCFe-WC-Co and NiCrSiBCFe-Cr3C2NiCr coatings

Hard coatings are used to improve the wear resistance of various engineering materials while maintaining the mechanical properties of the base material. In this work, the high-velocity oxy-fuel (HVOF) thermal spray process was used to deposit NiCrSiBCFe(65)-WC-Co(35) and NiCrSiBCFe(65)-Cr3C2-NiCr(35) coatings on SA213-T17 boiler steel to improve the erosion wear resistance of the base material. The erosion wear behaviours of the specimens were investigated using an air jet erosion tester at 30 and 90° impact angles and 400 ± 25 °C temperature. The surface morphologies of the as-deposited and eroded samples were examined using the Scanning electron microscope. The NiCrSiBCFe-WC-Co ceramic coating deposited on SA213-T17 boiler steel exhibited superior erosion resistance compared to NiCrSiBCFe-Cr3C2-NiCr coating and boiler steel under all the tested conditions. This enhanced performance can primarily be attributed to the higher hardness of the NiCrSiBCFe-WC-Co coating due to the presence of harder phases such as WC, W2C and NiCo2O4.

Microstructure, property and high-temperature wear performance of Cr3C2-based coatings deposited by conventional and ID-HVAF spray torches: A comparative study

The durability of industrial components exposed to high temperatures can be increased by depositing high-velocity air-fuel (HVAF) sprayed Cr3C2-based coatings. The uniform embedding of wear-resistant Cr3C2 within an oxidation-resistant binder matrix allows HVAF-sprayed Cr3C2-based coatings to be widely used in high-temperature environments. However, consolidating these coatings demands an optimum particle velocity and temperature combination, primarily dependent on the spray torch design. Understanding the role of spray torch variants with altered combustion chamber and nozzle designs is essential, which might influence the coating (splat) formation mechanism and the resultant wear performance. Accordingly, Cr3C2–25NiCr and Cr3C2–30NiCrMoNb were sprayed using different HVAF torches (high-power AK06 and low-power AK05-ID (inner diameter): generate different energy (thermal + kinetic) output) to understand the role of the binder as well as the torch design. The deposited coatings were comprehensively compared based on splat morphology, microstructure, mechanical properties, room and high-temperature erosion and sliding wear behavior. Subsequently, a detailed post-wear analysis was performed to decipher the associated wear mechanism. As inferred from the results, Cr3C2–25NiCr coatings deposited through a high-power AK06 spray torch displayed preferable microstructure, properties and superior wear resistance. The study also offered new insights into HVAF-ID torch-deposited coatings.

Study on the corrosion performance of supersonic atmospheric plasma sprayed Cr3C2-NiCr coatings

PurposeDue to the harsh underground environment in coal mining, the surface of hydraulic support columns corrodes severely, resulting in significant economic losses. Therefore, a highly corrosion-resistant coatings is needed to extend the service life of the columns.Design/methodology/approachThis study aims to compare the corrosion resistance of ST-Cr3C2-NiCr (sealed treatment Cr3C2-NiCr) coatings with industrially applied chromium plating. The corrosion failure mechanism of the coatings was investigated.FindingsThe results demonstrated that the ST-Cr3C2-NiCr coatings exhibited excellent corrosion resistance. After sealing treatment, the corrosion potential of Cr3C2-NiCr coatings was −0.215 V, and the corrosion current density of Cr3C2-NiCr coatings was lower than that of the plated parts.Practical implicationsST-Cr3C2-NiCr coatings prepared by supersonic atmospheric plasma spraying could provide excellent corrosion resistance in the coal industry.Originality/valueThe low porosity and the presence of the NiCr phase were crucial factors contributing to the preferable corrosion resistance exhibited by the ST-Cr3C2-NiCr coatings. The corrosive process of the coatings involved layer-by-layer delamination of surface oxide film, sub-surface pitting, formation and degradation of sub-surface passive film, as well as severe block-like delamination.

High Temperature Corrosion Performance of HVOF and D-gun Formulated Cr3C2-NiCr and Rare Earth Element Doped Cr3C2-NiCr Coating on TP347H Austenite Steel

High Temperature Corrosion Performance of HVOF and D-gun Formulated Cr3C2-NiCr and Rare Earth Element Doped Cr3C2-NiCr Coating on TP347H Austenite Steel

An HVOF-Sprayed (Cr3C2-NiCr+Co) Composite Coating on Ductile Cast Iron: Microstructure, Mechanical Properties, and Scratch Resistance.

High-velocity oxy-fuel (HVOF) thermally sprayed Cr3C2-NiCr coatings have been shown to be effective in shielding important machinery and equipment components from wear in harsh, high-temperature conditions. In this investigation, the HVOF thermal spray coating technique was used to deposit Cr3C2-NiCr powder with 10% Co particles onto ductile cast iron. The effect of the Co particles on the mechanical, tribological, and microstructure characteristics of a Cr3C2-NiCr/ductile cast iron system was investigated. The microstructure analysis employed various techniques, including light microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Scratch tests were applied to analyze the coating quality and adhesion. The coatings created using the HVOF spray method with Cr3C2-NiCr powders mixed with Co particles exhibited a dense structure containing large Co particles, partially melted, and very fine Cr3C2 particles embedded into the NiCr alloy matrix. Additionally, they possessed high hardness and excellent adhesion to the substrate. The results of bending strength tests were also presented, together with information on the coating's microhardness and fracture toughness. These included an analysis of the cracks and delamination in the Cr3C2-NiCr/ductile cast iron system. It was observed that the addition of Co particles significantly increased the resistance to cracking and wear behavior in the studied system.

Influence of High-Velocity Oxy-fuel Sprayed Cr3C2-NiCr Coating on Corrosion and Wear Properties of AISI 2205

Influence of High-Velocity Oxy-fuel Sprayed Cr3C2-NiCr Coating on Corrosion and Wear Properties of AISI 2205

Interaction mechanisms and high-temperature erosion-oxidation performance of Cr3C2-NiCrCoMo/nano-TiC coatings

To improve the erosion resistance of typical Cr3C2-NiCr coatings at high temperature, a novel Cr3C2-NiCrCoMo/nano-TiC (NCT) coating was developed and deposited by the high-velocity oxygen fuel spray (HVOF), which involved a cooperative modification of the multi-alloy binding phase and ceramic phase. This study delves into the influence of nano-TiC on the coating’s resistance to erosion under varying impact angles, particularly at 700 °C and 800 °C. Additionally, it explores the interaction between oxidation and erosion processes within the coating. The results indicated that the NCT1 coating with the addition of 3 wt% TiC features lower erosion rates of 1.97, 2.56, 3.14 mg/g under the impact angles of 30°, 60° and 90° at 700 °C, and 2.16, 2.87, 3.49 mg/g at 800 °C compared with original NCC coating. By comparison, the NCT2 coating with 6 wt% nano-TiC shows a deterioration in erosion resistance. The results show that at high temperatures, the erosion resistance of the coating changes from the micro-cutting at lower angles, to the brittle fracture and spalling at higher angles. The appropriate addition of nano-TiC supports and stabilizes the metal binding phase of the NCT1 coating. However, excessive nano-TiC in NCT2 coating contributes to the separation of coating phases during the erosion. The oxidation of the nano-TiC promotes the diffusion of Cr3+ ions, thus accelerating the coating oxidation and deteriorating the high-temperature erosion resistance eventually. The study is anticipated to enhance the longevity and the high-temperature erosion resistance of Cr3C2 cermet coatings, offering significant advancements in practical applications.

Effect of Structure Density of Milled Powder on Hot Corrosion and Erosion Resistance of HVOF-Sprayed Cr3C2-NiCr Coating

Effect of Structure Density of Milled Powder on Hot Corrosion and Erosion Resistance of HVOF-Sprayed Cr3C2-NiCr Coating

Development of Graphene Nanoplatelets Reinforced HVOF sprayed Cr3C2-NiCr Coatings

Development of Graphene Nanoplatelets Reinforced HVOF sprayed Cr3C2-NiCr Coatings

SPRAYING PROCESS FOR Cr<sub>3</sub>C<sub>2</sub>-NiCr COATING

In this paper, the theoretical research of Cr3C2-NiCr coating for zirconia substrate is discussed. To obtain this coating, one of the multi-efficiency methods high velocity oxygen-fuel thermal spraying (HVOF) was investigated. The coatings were processed by different thicknesses of zirconia substrate sample of 3–5 mm also with length of 20 mm and width of 30 mm, at spraying speed of 600–700 m/s. The temperature during HVOF spraying is about 3000 ºC and the cooling temperature is 27 ºC. Investigating the theoretical data of Cr3C2-NiCr coatings, the development and thermal stresses after HVOF treatment were determined using Stone's method and Brenner-Senderoff equations with a coating thickness not exceeding 0.6 mm for carbide coatings. According to the results of theoretical research, the deposition efficiency values were found by the method proposed by Kosaku Shinoda. According to the theoretical and mathematical calculations, the deposition efficiency for Cr3C2-NiCr coating with zirconia substrate is in the range of 59.5%–69.4%. Thus, it was found that the deposition efficiency for the coatings depends on the thickness of the substrate, the powder feed rate, and the mass of the applied material and consequently the number of spraying passes.

Effects of hBN content and particle size on microstructure, mechanical and tribological properties of NiCr-Cr3C2-hBN coatings

With a stable two-dimensional layered structure at high temperatures, hexagonal boron nitride (hBN) is considered a good solid lubricant in a wide temperature range. Adding hBN lubricating phase into NiCr-Cr3C2 coatings is expected to enhance the tribological properties of coatings and improve the compatibility between friction pairs. In this study, NiCr-Cr3C2-hBN composite powders with different hBN contents (3 wt%, 6 wt%) and particle sizes (1–2 μm, 15–45 μm) were prepared using a ball milling and spray granulation method. Subsequently, low-porous (1 %–4 %) and high-hardness (800-1200 HV) composite coatings were created using supersonic plasma spraying technology. The structure, phase, and chemical composition of the powders and coatings were analyzed using SEM, EMPA, and XRD characterization techniques. The mechanical and tribological properties of the coatings were also tested. Research findings reveal that supersonic plasma spraying successfully creates wide-temperature-range wear-resistant self-lubricating coatings with the hBN phase, effectively protecting GH4169 substrates. The properties of the coatings are influenced by the concentration and particle size of hBN. When the hBN content is excessively high, the tangential cohesive strength weakens, which negatively impacts wear resistance and rate. Larger hBN particles result in a mixed distribution, while smaller particles promote a uniform dispersion. The 3 wt% hBN (1–2 μm) coating exhibits optimal performance; however, the 3 wt% hBN (15–45 μm) coating may show improvement if its cohesive strength is enhanced by increasing the wettability of hBN.

Influence of Pulse-Plasma Treatment Distance on Structure and Properties of Cr3C2-NiCr-Based Detonation Coatings

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.

Laser re-melting of modified multimodal Cr3C2–NiCr coatings by HVOF: Effect on the microstructure and anticorrosion properties

Abstract Modified multimodal (MMP) Cr3C2–NiCr coatings were fabricated by high-velocity oxy-fuel (HVOF) spraying deposited on a CuCrZr alloy substrate. However, due to the lack of its inevitable porosity, an additional laser re-melting (LRM) approach is highly required to improve the coating performance. Therefore, the LRM technique is employed in this study to improve the microstructure properties of an MMP Cr3C2–NiCr coating by HVOF. Solid-state phase transformation from Cr3C2 to Cr7C3 occurred during the LRM process. After the LRM process, the coating exhibits the presence of Cr3C2 nanoparticles that serve as reinforcement. These nanoparticles demonstrate minimal lattice misfit and exhibit high stability throughout the LRM process. The surface of the coating undergoes modification, resulting in the formation of homogeneous nano (20–130 nm), micron (150 nm to 0.3 μm), and submicron (2–3 μm) Cr3C2 structures, along with high-density microstructures, after the LRM process. Nano-Cr3C2 particle reinforced with high total work function and incredibly increased corrosion rate significantly improves coating corrosion resistance. Overall, porosity decreased from 3.9% of the HVOF coating to 0.3% of the LRM. As a result, the current density of anticorrosion decreased from 33.7 to 4.35 µA·cm−2, and the Vickers microhardness average values ranged from 1,050 to 1,300 HV0.3, indicating improved microstructure development and related properties.

Prediction of In-Flight Particle Properties and Mechanical Performances of HVOF-Sprayed NiCr-Cr3C2 Coatings Based on a Hierarchical Neural Network.

High-velocity oxygen fuel (HVOF) spraying is a promising technique for depositing protective coatings. The performances of HVOF-sprayed coatings are affected by in-flight particle properties, such as temperature and velocity, that are controlled by the spraying parameters. However, obtaining the desired coatings through experimental methods alone is challenging, owing to the complex physical and chemical processes involved in the HVOF approach. Compared with traditional experimental methods, a novel method for optimizing and predicting coating performance is presented herein; this method involves combining machine learning techniques with thermal spray technology. Herein, we firstly introduce physics-informed neural networks (PINNs) and convolutional neural networks (CNNs) to address the overfitting problem in small-sample algorithms and then apply the algorithms to HVOF processes and HVOF-sprayed coatings. We proposed the PINN and CNN hierarchical neural network to establish prediction models for the in-flight particle properties and performances of NiCr-Cr3C2 coatings (e.g., porosity, microhardness, and wear rate). Additionally, a random forest model is used to evaluate the relative importance of the effect of the spraying parameters on the properties of in-flight particles and coating performance. We find that the particle temperature and velocity as well as the coating performances (porosity, wear resistance, and microhardness) can be predicted with up to 99% accuracy and that the spraying distance and velocity of in-flight particles exert the most substantial effects on the in-flight particle properties and coating performance, respectively. This study can serve as a theoretical reference for the development of intelligent HVOF systems in the future.

Tailoring microstructural features of Cr3C2-25NiCr coatings through diverse spray variants and understanding the high-temperature erosion behavior

Thermal sprayed Cr3C2-NiCr coatings are widely used to protect industrial components from ambient or elevated erosive degradation. Various thermal spraying techniques such as plasma spray, detonation spray (DS), high velocity oxy-fuel (HVOF) and high velocity air-fuel spray (HVAF) are widely used to deposit Cr3C2-NiCr coatings. The choice of thermal spraying technique governs the inflight particle velocity and temperature, resulting in unique coating microstructural features, characteristics and erosion performance. In this study, Cr3C2-NiCr coatings are deposited through HVAF, DS and axial plasma spray. A comprehensive comparative analysis was performed to understand the process-structure-property relationship of Cr3C2-NiCr coatings, which correlated with the room and high temperature erosion performance. HVAF spray deposited Cr3C2-NiCr coatings with preferred microstructural features and properties, ensuring superior (high/room temperature) erosive resistance. Cr3C2-NiCr coatings deposited via DS spray performed second best, while plasma sprayed exhibited defective microstructure with inferior mechanical properties, resulting in substandard erosion performance.