Cr3C2-NiCr Coatings Research Articles

Effects of modification of hBN by nickel plating on coating structure and properties of supersonic plasma spraying NiCr-Cr3C2-hBN@Ni coatings

Hexagonal boron nitride (hBN) with excellent self-lubrication performance is expected to relieve the friction resistance and wear of NiCr–Cr3C2 coatings. However, the poor wettability of hBN with most materials makes it difficult to fabricate NiCr–Cr3C2-hBN composite coating with good cohesion strength. In this study, hBN was firstly pretreated through magnetron-sputtering aided Ni plating to form hBN@Ni particles. Then, NiCr–Cr3C2-hBN@Ni powder was prepared by spray granulation. Next, corresponding coatings were prepared through supersonic atmosphere plasma spraying. It was found that in comparison with NiCr–Cr3C2-hBN coating, the NiCr–Cr3C2-hBN@Ni coating exhibited a decreased porosity (from 3.6% to 0.3%), elevated cohesion (from 52.78 N to 62.11 N), and the wear rate decreased by an order of magnitude. It was concluded that hBN@Ni can effectively improve the component interface inside powder, enhance the cohesion of molten in-flight particles, and make the internal structure of the coating denser.

Role of micro- and nano-CeO2 reinforcements on characteristics and tribological performance of HVOF sprayed Cr3C2-NiCr coatings

The present study investigates the role of micro- and nano-CeO2 reinforcements on microstructural, mechanical and tribological properties of Cr3C2-NiCr coatings deposited using high-velocity-oxy-fuel (HVOF) spray process. A novel blending method involving ultrasonication, magnetic stirring and 3D-tumbler mixing was used to prepare the micro- and nano-CeO2 reinforced Cr3C2-NiCr feedstock powders. Unreinforced Cr3C2-NiCr coatings were also prepared for comparison purposes. X-ray diffraction, FE-SEM, EDS mapping, optical microscopy and optical profilometry were used to characterize the coatings. Tribological studies were performed on the coatings using modular ball-on-disc tribometer. The results showed that nano-CeO2 reinforced coatings yielded considerable reduction in porosity, surface roughness and CoF values while significantly enhancing the hardness and fracture toughness in comparison to the micro-CeO2 reinforced and unreinforced Cr3C2-NiCr coatings. The addition of nanoCeO2 to the coatings contributed to the microstructure refinement and to the formation of stable tribo-oxide layer, resulting in a lower specific wear rate under identical test conditions. Performance of micro-CeO2 reinforced coatings was intermediate to that of nano-CeO2 reinforced and unreinforced Cr3C2-NiCr coatings.

Mechanical properties optimization of Cr3C2-NiCr coatings produced by compact plasma spray process

Chromium carbides are widely used as functional coatings on steel structures in high-end applications, from energy to marine and aerospace sectors thanks to their corrosion and wear resistance at elevated temperatures. In the present work, a low-power compact plasma spray (CPS) equipment was used to deposit Cr3C2-based cermet coatings on carbon steel substrate. Design of experiment was applied to select and optimize the spraying parameters, namely current, stand-off distance, scanning speed, plasma gas rate and powder feeding rate. ANOVA analysis was conducted to estimate the effect of the spraying variables on morphology and mechanical properties of the coatings and evaluate the optimal spraying condition. Dense and compact coatings were fabricated by using the CPS. By optimizing the processing parameters, coating hardness equal to approximately 600 HV and average thickness ranging around 600 μm were obtained, while the adhesion strength was approximately equal to 14 MPa. Intermediate phases of Cr carbides were produced by the dissolution of the primary Cr3C2 induced by melting and re-solidification of the particles. The presence of weaker carbide phase, inter-lamellae different features and porosity also caused the scattered hardness values observed in the coatings.

Influence of processing condition and post-spray heat treatment on the tribological performance of high velocity air-fuel sprayed Cr3C2-25NiCr coatings

In the present study, fine and coarse Cr3C2-25NiCr particles were sprayed through HVAF and oxygen-augmented HVAF(O) modes. The as-deposited coatings were heat treated in order to improve the microstructural features and mechanical properties. The as-deposited and heat-treated coatings were characterized in detail for their phase composition, microstructural features and mechanical properties. Subsequently, a high-load sliding test (ball-on-disc) was performed to evaluate the influence of processing conditions and heat treatment on the sliding wear performance of Cr3C2-25NiCr coatings. Following that, detailed post-wear analyses were performed to analyze the wear rate/mechanism. As inferred from the results, the appropriate choice of process parameters and heat treatment conditions improved the sliding wear performance of Cr3C2-25NiCr coatings.

Contact fatigue properties of NiCrCr3C2 and AlSi coatings for sealing performance of the Wankel engine

NiCrCr3C2 and AlSi coatings were prepared using supersonic plasma equipment. The contact fatigue properties of the coatings were evaluated under dry friction, fuel oil, and lubricating oil conditions. The fatigue life of the NiCrCr3C2 coating was much longer than that of the AlSi coating at the same pressure. Under the same conditions, the NiCrCr3C2 coating had better contact fatigue performance than the AlSi coating, and due to the wettability of Cr3C2 and NiCr alloys, the Cr3C2 hard phase was firmly embedded in the NiCr alloy to ensure hardness and wear resistance at high temperatures.

Influence of Spraying Parameters on the Structure and Tribological Properties of Cr3C2-NiCr Detonation Coatings

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.

Structural characteristics and wear, oxidation, hot corrosion behaviors of HVOF sprayed Cr3C2-NiCr hardmetal coatings

It is of great importance to determine the wear, oxidation, and hot corrosion behavior of thermally sprayed Cr3C2-NiCr hardmetal coatings under different conditions, which are widely used in the different industrial applications. In this study, the influence of damage mechanisms such as oxidation, hot corrosion, and wear of Cr3C2-NiCr hardmetal coatings on stainless steel substrates at different temperatures and time periods was investigated. The properties of the coated samples were examined using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and 3D-optical surface profilometry. Increased time at oxidation tests has indicated that different oxide formations was accelerated by the effect of temperature. It is identified that changes have occurred in the microstructure of the Cr3C2–NiCr coatings depending on high temperature and time. At the oxidation tests, the oxidation layer was increased as a function of time. As a result of the hot corrosion effect, the Na2SO4 and V2O5 powder mixtures melted with the effect of temperature, leaked from the micro cracks, pores and moved from the coating surfaces to the inner regions. The Cr2O3 structure formed as a result of the temperature effect on the coating surface showed a protective feature, increasing the resistance of the coating against oxidation and delaying the formation of damage. Findings from the wear test indicated that the relative sliding motion of the surfaces in contact with the movement of the applied load results in shear stress, which causes friction force to be generated. The friction coefficients increase depending on the load, and as the load increases, resulting in volume losses.

Electrochemical corrosion and solid particle erosion response of Y2O3 dispersed FeAl coatings deposited by detonation spray

The electrochemical corrosion and erosion wear behaviors of detonation sprayed ODS FeAl powder coatings on T91 substrate were investigated. Electrochemical corrosion resistance of the deposited coatings was evaluated in three different aqueous media, namely 3.5 wt% (0.61 M) NaCl, 2 N (1 M) H2SO4 and 3.5 wt% (0.25 M) Na2SO4 and are compared with T91 substrate and detonation sprayed Cr3C2–25NiCr coatings (on T91 substrate). The ODS FeAl coatings shown improved corrosion resistance in 3.5 wt% Na2SO4 than T91 substrate. However, the Cr3C2–25NiCr coatings have shown consistently better corrosion resistance than T91 substrate and ODS FeAl coatings in all the aqueous media. The corrosion mechanisms investigated imply that the higher corrosion rate of FeAl coatings as compared to the Cr3C2–25NiCr coatings is well compensated by the uniform corrosion in the case of former than the localized and intense corrosion in the case of later coatings and substrate material. In contrast, the solid particle erosion wear studies conducted at two different temperatures namely, room temperature (25 °C) and 400 °C have revealed that the ODS FeAl coatings exhibited 4 to 5 times improved wear resistance than that of Cr3C2–25NiCr coatings at room temperature and 1.5 to 2.5 times at a higher temperature (400 °C). Also, the ODS FeAl coatings have performed marginally better than the T91 substrate at both the test temperatures. The results obtained together with the observations made demonstrate a leap step towards the development of novel thermal spray grade feedstock materials as an alternative to industrially well-known Cr3C2–25NiCr coatings and open up a new avenue of techno-economic benefits that can be further explored.

Effect of stoichiometry conditions on the erosion and sliding wear behaviors of Cr3C2-NiCr coatings deposited by a novel ethanol-fueled HVOF process

In this work, a novel ethanol-fueled HVOF process, as the most recently developed liquid fuel HVOF technology, was employed to prepare Cr3C2–25wt%NiCr hard-metal coatings on 304 stainless steel substrates. The influence of different stoichiometry conditions, defined as the oxygen/ethanol ratio, on the evolution of the coating microstructure was investigated in order to correlate with the properties of as-deposited Cr3C2–NiCr coatings. The results showed that the varied stoichiometry factors have little effect on the phase composition of the coating. However, they have a great influence on the microstructure and performances, including porosity, microhardness, fracture toughness, erosion resistance and sliding wear resistance. A denser Cr3C2–NiCr coating with higher erosion resistance is obtained when the stoichiometry factor is <1, being markedly different compared with the results obtained using kerosene-fueled HVOF processes. The stoichiometry factor of kerosene-fueled HVOF processes is generally slightly >1 allowing to obtain a higher quality Cr3C2–NiCr coating. The sliding wear mechanism of Cr3C2–NiCr coatings is attributed to abrasive grooving, peelings induced by cracking, fragmentation and pull-out of carbide grains, as well as delamination and tribo-oxidation.

HVAF vs oxygenated HVAF spraying: Fundamental understanding to optimize Cr3C2-NiCr coatings for elevated temperature erosion resistant applications

High velocity sprayed Cr3C2-NiCr coatings are a viable solution to improve the life of power plant components and are often influenced by the choice of processing conditions. The new generation convertible high-velocity air-fuel (HVAF) process offers higher versatility to spray wide ranging particle sizes including the standard high-velocity oxy-fuel (HVOF) grade. However, the use of such oxygenated spraying termed as ‘HVAF(O)’ mode necessitates better understanding for reliable and repeatable coating. Single particle splat morphology and fracture mechanisms of HVAF and HVAF(O) sprayed Cr3C2-NiCr coatings were correlated with the microstructural features, mechanical properties and erosion performance with two different particle sizes. Among the coatings studied, HVAF(O) sprayed coarse Cr3C2-NiCr and HVAF sprayed fine Cr3C2-NiCr provided the least thermal degradation, and better mechanical properties which collectively ensured enhanced erosion performance. The overall coating performance can be attributed to the appropriate choice of process conditions and suitable particle size. In comparison with conventional HVOF process that generally induces a certain degree of thermal degradation within the hard carbides, oxygenated HVAF(O) sprayed Cr3C2-NiCr coating still retained most of the starting carbide phase with minimal thermal degradation, which resulted in superior erosion performance.

Role of process parameters on microstructure, mechanical properties and erosion performance of HVAF sprayed Cr3C2-NiCr coatings

In this study, Cr3C2-NiCr coatings of two different particle sizes (fine: 10–30 and coarse: 15–45 μm) were deposited by variable nozzle lengths (long, medium and short) and profiles (convergent-divergent, over-expanding and straight barrel) using high-velocity air-fuel (HVAF) and oxygen augmented air-fuel (HVAF(O)) spray mode. A comparative analysis of the generated coating specimen was performed through the microstructural features, phases present, properties and erosion performance. Additionally, the deposition efficiency (DE) was evaluated to assess the techno-economic feasibility of HVAF/HVAF(O) sprayed Cr3C2-NiCr coatings. All the deposited coatings were dense, uniform and displayed a homogenous distribution of carbides. The convergent-divergent-based long and medium nozzle sprayed coatings displayed better mechanical properties, whereas coatings deposited by short-length nozzles showed relatively inferior properties. In terms of particle size, fine Cr3C2-NiCr sprayed using HVAF and coarse Cr3C2-NiCr sprayed using HVAF(O) displayed improved coating characteristics and properties. Erosive studies implied coatings with improved intersplat adhesion exhibited ductile eroding behavior like “ploughing” and “micro-cutting” rather than “splat flaking/chipping.” Overall, employing a medium-length, convergent-divergent nozzle deposited Cr3C2-NiCr coatings with an ideal combination of DE, mechanical properties and erosion performance. Besides, short-length nozzles were inappropriate for spraying Cr3C2-NiCr since they displayed compromised coating characteristics and performance.

High temperature erosion behaviour of high-velocity oxy-fuel sprayed CNT/NiCr-Cr3C2 composite coatings

In the present work, the effect of different weight percentages of carbon nanotubes on the high-temperature erosion behaviour of NiCr-Cr3C2 composite coatings is demonstrated. The high-velocity oxy-fuel (HVOF) spraying process was employed for the deposition of coatings on ferritic low-alloy steel (SA-213 T12). The solid particle erosion test of the coating with and without carbon nanotubes was conducted at a temperature of 600 °C with 30, 45, 60, and 90° impact angles using Al2O3 erodent particles. This work exhibited high erosion resistance for composite coatings with the highest CNT content of 7 %. However, as the impact angle was increased from 30° to 90°, the erosion rate of all coatings, irrespective of CNT content, increased. An Optical 3-Dimensional Profilometer was used to estimate lower crater depths for lower impact angles and deeper crater depths for higher impact angles observed through surface topography. The effect of the addition of CNTs in NiCr-Cr3C2 coatings resulted in a reduction in weight loss and erosion rate at different angles of impingement working under high temperatures. The outstanding mechanical properties of CNTs impart improved erosion resistance.

Ceria-Doped Cr3C2–NiCr Coatings on Austenite Steel for Investigation in Actual Boiler Environment

Ceria-Doped Cr3C2–NiCr Coatings on Austenite Steel for Investigation in Actual Boiler Environment

Laser Surface Alloying of Sintered Stainless Steel.

A characteristic feature of sintered stainless steel (SSS) is its porosity. Porosity results in a lower density of steel, making attractive components for producing lightweight structures and materials used in industry (e.g., the automotive industry or aerospace). Scientists also observe that porosity adversely affects steel’s properties, especially its strength properties. One of the proposals for improving the discussed properties is the use of surface treatment of sintered stainless steels, e.g., with the use of concentrated energy sources such as plasma beams or laser beams. However, this proposal is an incidental subject of research, which is not justified from the point of view of the obtained research results presented by a few research groups. In this study, the surface modification (surface treatment) of sintered stainless steel was presented. The authors proposed the use of two surface treatments in order to compare them and obtain the best results. The first treatment was the deposit of Cr3C2–NiCr coatings on SSS surfaces using the atmospheric plasma spraying (APS) method. The second treatment was to create surface layers on SSSs by laser alloying the surface with a CO2 laser. Due to high precision and ease of automation, the most common methods in surface alloying treatment are laser technologies. This research’s main aim was to analyze the microstructure and strength properties of the SSS surface layer. The research confirms that applying the Cr3C2–NiCr coating and modifying the surface layer through the laser alloying method improves the mechanical properties of SSSs.

Deposition mechanisms and characteristics of nano-modified multimodal Cr3C2–NiCr coatings sprayed by HVOF

Abstract Nano-modified multimodal and conventional Cr3C2–NiCr coatings were fabricated by high-velocity oxygen-fuel spraying deposited on CuCrZr substrates. Results showed that individual nano-modified multimodal Cr3C2–NiCr particles were composed of nano (25−180 nm), submicron (200 nm to 0.5 μm), and micron (2–4.5 μm) Cr3C2 grains, NiCr binder phases, and a tiny amount of rare earth oxide additives. The nano-modified multimodal Cr3C2–NiCr coatings maintained a unique structure: submicron Cr3C2 grains embedded in the voids formed by micron Cr3C2 grains, NiCr binder phases and nano Cr3C2 grains imbedded in the voids formed by submicron and micron Cr3C2 grains, and nano Cr3C2 grains are dispersed in NiCr metal binder phases. A few discontinuous elongated amorphous and nanocrystalline phases existed in them. The mechanical interlocking was the dominant bonding mechanism accompanied by local metallurgical bonds. Compared to the conventional coating, the multimodal coating was uniform and dense (porosity was 0.3 ± 0.12%) as well as not obvious lamellar structures, the adhesive strength was 75.32 ± 1.21 MPa, exhibiting a 65 pct increase, and the microhardness was increased by about 18%. The lower porosity and higher strength of nano-modified multimodal structure coating were mainly related to dispersion distribution and synergistic coupling effects of Cr3C2 hard grains with different scales.

Oxidation performance of TP347H superheater steel after depositing ceria-doped Cr3C2–25NiCr coatings

Oxidation performance of TP347H superheater steel after depositing ceria-doped Cr3C2–25NiCr coatings

Slurry erosion behavior of thermally sprayed ceramic nanocomposite coatings on turbine steel

AbstractThe aim of the present study is to investigate the slurry erosion behavior of nano‐yttria‐stabilized zirconia (YSZ) reinforced Cr3C2–25NiCr ceramic nanocomposite coatings deposited on turbine steel. The Cr3C2–25NiCr coating powder, 95% (Cr3C2–25NiCr) + 5% YSZ, and 90% (Cr3C2–25NiCr) + 10% YSZ nanocomposite coating powder deposited on CA6NM steel samples by using high‐velocity oxy‐fuel coating technique. L9 orthogonal array Taguchi method was used to design the experiment. Erosion tests were performed on erosion test rig under hydro accelerated conditions at different levels of various parameters. Erosion tests and analysis of variance resulted that for coated samples, velocity is the major influencing factor followed by slurry concentration, impact angle, and particle size. Velocity was the largest contributor to the mass loss, whereas particle size has the least contribution to mass loss of the coated samples. The scanning electron microscopy analysis of eroded samples revealed that craters, micropores, platelets, plowing, spalling, and so on were responsible for the mass loss of uncoated and coated samples. The incorporation of YSZ nanoparticles decreased the porosity; erodent particles cannot penetrate more deeply inside the workpiece and resulted in less erosion. It has been resulted that 95% (Cr3C2–25NiCr) + 5% YSZ and 90% (Cr3C2–25NiCr) + 10% YSZ ceramic nanocomposite coatings exhibited better erosion resistance as compared to Cr3C2–25NiCr coatings due to high microhardness and low porosity.

Characterization and High-Temperature Fretting Wear Resistance of HVOF-Sprayed Cr3C2-NiCr, CoCrWC and CoCrWNiC Hardfacing Coatings

Characterization and High-Temperature Fretting Wear Resistance of HVOF-Sprayed Cr3C2-NiCr, CoCrWC and CoCrWNiC Hardfacing Coatings

Optimization of Plasma Spraying Parameters with Respect to Shear Adhesion Strength of Cr3C2-NiCr Coating on 16Mn Steel

Optimization of Plasma Spraying Parameters with Respect to Shear Adhesion Strength of Cr3C2-NiCr Coating on 16Mn Steel

Experimental investigation on effect of water jet erosion parameters on HVOF sprayed Cr3C2-NiCr coatings on stainless steel: a mathematical approach

Chromium carbides are major components in turbine blades due to their high wear resistance, low friction coefficient, and corrosion resistance at high temperature, typically manufactured by thermal spraying for coating applications. For their excellent oxidation and corrosion tolerance, high-speed thermal spray cermet coatings are commonly used to reduce wear at high temperatures and in corrosive conditions. Coatings based on Cr3C2-NiCr have been deposited by means of the HVOF thermal spraying technique on an AISI 304 steel substrate. Furthermore, the erosion behavior of the substrate and coated samples was tested using a water jet erosion test. The effect of water jet parameters, including angle of impingement, water jet velocity, standoff distance, and erodent discharge, on the erosion rate was systematically investigated. Experiments were conducted on the basis of the core composite architecture and the surface response approach for the creation of multiple regression models. Through the analysis of variance, the precision of the regression models was sufficient to establish associations between input parameters and responses. Results revealed that the most prevailing factor impacting the erosion rate of the coatings, followed by water jet velocity, standoff distance, and eroding discharge, was the angle of impingement.