Cermet Powders Research Articles

Advancement in cermet based coating on steel substrate: A review

Ceramic and metals mixed phases are a category of materials known as cermet to produce materials that have the best characteristics of both such as high hardness, abrasion wear resistance, resistance to corrosion-erosion resistance and deformation resistance against high temperature. Several thermal spray procedures e.g., high velocity air or oxygen fuel, spraying by plasma, detonation gun, and other cladding techniques, such as laser cladding, Tungsten inert gas arc cladding, have been widely utilised for the cladding of cermet powders on steel in recent decades. Cermet-based coatings on steel have gained popularity in recent years as a potential approach for improving metallurgical, mechanical, corrosion, erosion, and wear properties. This paper summarises the research that has been done to create cermet coating on steel.

Microstructure Investigation of WC-Based Coatings Prepared by HVOF onto AZ31 Substrate

In this paper, three commercial cermet powders, WC-Co-Cr, WC-Co and WC-Cr3C2-Ni, were sprayed by the High Velocity Oxy Fuel (HVOF) method onto magnesium alloy AZ31 substrate. The coatings were investigated in terms of their microstructure, phase analysis and residual stress. The manufactured coatings were analyzed extensively using optical microscopy (OM), X-ray diffraction (XRD), scanning (SEM) and transmission electron microscopy (TEM). Based on microstructure studies, it was noted that the coatings show satisfactory homogeneity. XRD analysis shows that in WC-Co, WC-Co-Cr and WC-Cr3C2-Ni coatings, main peaks are related to WC. Weaker peaks such as W2C, Co0.9W0.1, Co and W for WC-Co and W2C, Cr3C2 and Cr7C3 for WC-Cr3C2-Ni also occur. In all cermet coatings, linear stress showed compressive nature. In WC-Co and WC-Cr3C2-Ni, residual stress had a similar value, while in WC-Co-Cr, linear stress was lower. It was also proved that spraying onto magnesium substrate causes shear stress in the WC phase, most likely due to the low elastic modulus of magnesium alloy substrate.

Effects of different HVOF thermal sprayed cermet coatings on tensile and fatigue properties of AISI 1045 steel

The objective of the present work was to investigate the effect of different cermet coatings on tensile and high-cycle fatigue properties of AISI 1045 steel using High-Velocity Oxygen Fuel (HVOF) thermal spray process. In this study, the WC-12Co, WC-10Co-4Cr, and Cr3C2–25NiCr cermet powders were coated onto the surface of annealed AISI 1045 steel specimens via the HVOF thermal spray process. The corresponding HVOF thermal spraying results were compared with those obtained from hard chrome (Cr) electroplating process. The thermal spray coated specimens showed load drop tendency beyond the yield point with significant work hardening in the tensile results, but low fatigue life than the base material in high-cycle fatigue results due to defects and poor adhesion at the interface. However, those cermet coating materials showed higher fatigue strengths than the hard chrome plated material. Fractography tests showed that fatigue strength was not only dependent on residual stress, but also influenced by the modes of fatigue failure related to the coated layer's cohesion and adhesion strength. Overall, the Cr3C2–25NiCr cermet coating is preferable due to its less porosity, high fatigue property, and better adhesion than the other coated materials.

Optimization of Coating Process from Cermet Powders by Plasma Spraying in Air

The paper presents studies on the optimization of the process of applying coatings from cermet powders with different solid phase contents by plasma spraying in air to restore and harden parts of machines and mechanisms operating under adverse conditions. Such conditions are usually created in heavily loaded tribojoints when the mechanisms operate at a low speed of relative movement of surfaces during friction. At the same time, the destruction of the working surfaces is mainly due to the process of microcontact setting and subsequent detachment of the formed particles at their contact points. The application of special protective coatings with the required properties is possible with the manufacture of high-quality starting powder materials and optimization of the technology for their application. Such powders and powder compositions can be obtained by the method of agglomeration of a fine powder mixture with its subsequent high-temperature sintering. To identify the hardening mechanism of composite coatings made of cermet by gas-thermal spraying, important stages are the optimization of the deposition process parameters and the study of the properties of plasma coatings obtained in this case. When optimizing the technological parameters of plasma spraying of coatings, the utilization rate of the sprayed powder material has been taken into account as the main indicator of the process efficiency, the structure of the obtained layers, and the morphology of individual particles deposited on the polished surface. The paper provides data on the structural elements of sprayed materials for wear-resistant coatings obtained by plasma spraying at optimal conditions. Taking into account the processes that occur during the wear of tribological conjugations, the data indicate the existing prerequisites for the wear resistance of the studied composite coatings made of metal ceramics. Special wear-resistant coatings made of materials with a soft matrix hardened by solid inclusions Al2O3–TiO2–Ni–Cr–Al–Y are widely used in various industries. Based on the detailed analysis of the features of cermet plasma coatings, it can be stated that such powder compositions (complex oxides-metal component) are often used as wear-resistant plasma coatings. The research results can be taken into account in cases of application of wear-resistant plasma coatings made of metal-ceramics and compositions based on them, containing solid phases in the form of oxides, as well as the manufacture of a whole range of parts operating under conditions of intense wear.

Preparation, mechanical properties and enhanced wear resistance of TiC-Fe composite cermet coating

TiC-Fe based cermet coating with high hardness and superior wear resistance together with low price and environmental friendliness was developed. Initially, the TiC-Fe composite particles were prepared by high energy ball milling, spray drying and plasma spheroidization. These cermet powders not only showed high sphericity and dense microstructure but also presented homogeneous distribution of TiC. Then, the TiC-Fe cermet coating was deposited by high velocity air fuel (HVAF). The results indicated that introducing ceramics would increase the deformation degree of the splats and eliminate the layered structure, which effectively enhanced the microhardness and wear resistance of composite coating. Compared with pure metallic coating, the microhardness of cermet coating increased to 887.5 HV0.3, while the wear rates of cermet coating reduced by 40% and 60% at 10 N and 25 N, respectively. Besides, the TiC-Fe cermet coating showed much less sensitive to the heavy load. The primary wear mechanism of single 316 L coating was a combination of adhesive wear and severe oxidation, while the TiC-Fe cermet coating showed slight abrasive wear combined with oxidation. The excellent wear resistance together with its harmless to human body make the TiC-Fe based composite coating a potential candidate when using at kitchen ware surface.

Treatment of Turbine Blades via Cr2O3-Ni5%Al System Using Plasma Thermal Spraying

A plasma thermal spraying method was used for the purpose of coating the pre-prepared surfaces of turbine blades. Chromium oxide (Cr2O3) was used as a matrix reinforced with a metal material of Ni-5%Al at rates of 10, 20, 30, 40 and 50. The cermet powders were stirred for one hour then used to coat bases of steel (316L). A spray distance of 8cm was applied, and the binding material of Ni-22%Cr-10%Al-1%Y was sprayed with a thickness of 100μm. Then, the reinforced matrix was sprayed with a thickness of 300–350μm and the final thickness of the samples prepared was 400–450μm. The samples produced were sintered at 900°C for an hour and a half and underwent a hardness test, which gave the best hardness of the samples after sintering at a reinforcement rate of 50% by 612Hv. The lowest porosity value for the above rate was obtained at 3.88%. The results of the adhesive strength gave a value of 31.5 MPa after sintering and at the same 50% reinforcement. The results of the scanning electron microscope (SEM) showed that there was weakness and cracking in the coating layers at the low reinforcement ratios. However, the mechanical and physical properties improved with the increase in reinforcement ratios to reach the highest value of 50%. KEYWORDS Adhesion force, ceramites, scanning electron microscope, Vickers hardness

Strengthening of solid solution (Ti,La)(C,N)-based cermets by LaB6 addition

(Ti,La)(C,N)-based solid solution cermets are fabricated from self-prepared (Ti,La)(C,N) carbonitrides by powder metallurgy with LaB6 addition in the solid solution. Based on the results of XRD and SEM analyses, it is confirmed that there is complete dissolution of (Ti,La)(C,N) powder. The presence of La can effectively suppress grain overgrowth and thus enhance the homogeneity of porcelain microstructure, consequently increasing the particle size of black phase. On the basis of equal mass fraction of La, the performance of (Ti,La)(C,N)-based cermets is better than that of Ti(C,N)-La-based cermets prepared by simple addition of LaB6 to Ti(C,N)-based cermet powder. The discrepancy can be directly related to the effect of adding LaB6 in the solid solution. The physical and mechanical properties of (Ti,La)(C,N)-based cermets comes to optimum when the content of dissolved La is 0.25 wt%, and there is hardness elevation of 20%. With suitable La addition, there is decrease of oxygen content in the solid solution of cermets. It is hence deduced that LaB6 can improve the performance of cermets as a deoxidizer.

Mechanical and wetting properties of 25%NiCr-75%Cr2C3 cermet coated on low carbon steel using HVOF thermal spray technique

The hydrophobic ceramic–metal composites with enhanced mechanical properties will have longer durability because of the embedded liquid-repellent properties, with low water and salt absorption. In this work, the 25%NiCr-75%Cr2C3 cermet powder has been coated on low carbon steel substrate, using High Velocity Oxy-fuel thermal spray technique. The SEM is employed to analyse the morphological characterization of the coating. The mechanical properties of the 25%NiCr-75%Cr2C3 coating is evaluated using the Vickers micro-indentation technique. The micro-hardness, fracture toughness and brittleness index of the coatings are obtained. Also, the wetting property of the coating in 3.5% NaCl salt solution is investigated using the contact angle measured by sessile drop method. The contact angle of the coating is observed to be hydrophobic in nature with a contact angle of 98.14⁰. Thus, 25%NiCr-75%Cr2C3 hydrophobic coatings helps in the improvement of brittleness, fracture toughness, and the microhardness.

The milling effect of a new horizontal attrition milling in the production of (Ti0.7,W0.3)C–Ni cermet

The mechanical alloying (MA) method is a powerful and practical process to fabricate advanced materials with unique properties. Developing an effective milling process to produce high-quality powder suitable for scale-up is one of the main issues for the MA method. This study introduces a new high energy ball milling technique, the horizontal attrition ball milling (HAM). The milling effect of the HAM is superior to that of the conventional planetary and attrition milling techniques in the size reduction of particles (fragmentation) and the impact of milling (mechanical strength). The ultrafine (Ti0.7,W0.3)C–Ni cermet powders can be obtained by the HAM since (Ti0.7,W0.3)C particle growth is effectively inhibited during the carbothermal reduction. Sintered (Ti0.7,W0.3)C–Ni cermet by the HAM has excellent mechanical properties (hardness and fracture toughness). This study demonstrates that the newly designed HAM is a practical method for synthesizing ultrafine ceramic and composite powders appropriate to produce structural ceramics and composites that have excellent mechanical properties.

A review: 3D printing of microwave absorption ceramics

AbstractAlong with extensive research on the 3D printing and microwave absorption ceramics, 3D printing technology provides a great possibility for microwave absorption ceramics with arbitrary shapes in a faster, cheaper and more flexible way. This review focuses on the latest evolution in the raw materials, the structure design and the advanced additive manufacturing technologies of 3D printing microwave absorption ceramics. Firstly, the representative raw materials are divided into three categories, including ceramic powder, cermet powder and precursor resin. In addition, additives give rise to improvement of microwave absorption properties of ceramics. Secondly, based on two attenuation theories, structure design makes further efforts to enhance the microwave absorption performance of ceramics. Finally, comparisons are made between diversified manufacturing technologies to facilitate the selection of the best ones for different application in practical use. This study presents a summary of research that has been conducted to produce microwave absorption ceramics by additive manufacturing.

Microstructure and mechanical property of high velocity oxy-fuel sprayed multimodal WC-Cr3C2–Co–Y2O3 cermet coating

To investigate the effect of Cr3C2 and Y2O3 additions on cermet coatings, agglomerated and sintered multimodal WC-10Cr3C2–12Co and WC-10Cr3C2–12Co–1Y2O3 cermet powders were deposited as new type of WC-based cermet coatings on plain carbon steel substrate by high velocity oxy-fuel flame spraying. Microstructures, phases, and mechanical properties of both WC-10Cr3C2–12Co and WC-10Cr3C2–12Co–1Y2O3 coatings were examined and compared with those of WC-12Co coating. Results showed that WC-10Cr3C2–12Co and WC-10Cr3C2–12Co–1Y2O3 cermet coatings presented homogeneous microstructures with multimodal carbide particles well distributed in binder matrix, and exhibited phases similar to the feedstock without decomposed phase. However, WC-12Co coating showed the existence of some serious decomposed phases including W2C and amorphous Co3W3C. Morphologies of individual splats on WC-Co substrate clearly demonstrated liquid–solid two phase deposition behaviors of three types of powders in which carbide particles were mainly present in solid state and Co in liquid state. Furthermore, fracture toughness, elastic modulus, and wear resistance of WC-10Cr3C2–12Co and WC-10Cr3C2–12Co–1Y2O3 coatings were found to be higher than those of WC-12Co coating owing to synergistic effects of Cr3C2, Y2O3, and multimodal carbides. Surface morphologies of worn out WC-12Co, WC-10Cr3C2–12Co, and WC-10Cr3C2–12Co–1Y2O3 coatings indicated that wear mechanism mainly included gouging and peeling off.

Design of core-shell structured YSZ@Cu cermet powders with thermal conductivity anisotropy by electroless deposition

Core-shell structured cermet powders with thermal conductivity anisotropy have been brought into focus because they have a great potential application as the horizontal thermal diffusion layer material in multilayer thermal protective coating (TPC). In this contribution, core-shell structured YSZ@Cu cermet powders were fabricated by electroless deposition (ED) of Cu on yttria-stabilised zirconia (YSZ) powder. The surface of YSZ powder was uniformly coated with a thin Cu shell of approximately 2 μm. Through X-ray photoelectron spectra (XPS) analysis, it was found that trace CuO and Cu2O oxides formed on the surface of Cu shell. Results of thermal spraying adaptability analysis show the flowability of core-shell structured YSZ@Cu cermet powder improved to 56.8 s/50 g, which conforms better to the basic requirements of thermal spraying material. By differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) tests, the YSZ@Cu powder had good thermal stability. In particular, between 25 and 500 °C, the anisotropy thermal conductivity rose higher than 1.8 and it remained stable at approximately 1.6 with temperature as high as 900 °C. All these features promise it a high-performance thermal conductivity anisotropy material.

Effect of Powder Mixture Composition on the Deposition Efficiency in Cold Spay: Modelling and Experimental Validation

In this paper, a new semiempirical probability model, allowing for prediction of the composition of multimaterial cold spray coating in dependence on the initial percentage of blend components, is developed and applied. The proposed modeling approach takes into account the deposition efficiencies and the particle sizes of each component of the spraying powder blend. The experimental validation using several Cu/Cr2C3NiCr mixtures with different percentages of copper and cermet powders showed that the simulation results were in a good agreement with the experimental data. It was demonstrated that the deposition efficiency of the Cr2C3NiCr cermet powder strongly decreased when its mass percentage in the Cu/Cr2C3NiCr mixture increased from 5% to 75%. It was also shown that the dependence of the Cr2C3NiCr content in the coating on the initial percentage in the blend was nonlinear and the standard rule of mixtures was not applicable for prediction of copper–cermet coating composition.

Wear behaviour of plasma sprayed WC−12%Cο and Al2O3−13%TiO2 coatings on ASTM A36 steel used for I.D. fans in coal fired power plants

Erosion is a major problem for the power generation plants for any country. A very high cost induced per annum accounting for the downtime of replacement/repair of boiler components of coal fired power plants due to oxidation and erosion.Thermal spray coating technique is a method used for coating the mechanical components in order to enhance the surface properties of the base material like resistance to corrosion, wearand erosion. In the present study, the cermet powders and coatings (wt% age) are applied on steel substrate with the help of plasma spray gun technique. Techniques like XRD, SEM/EDX and EPMA analysis have been used for characterization of the coatings. These coated materials were subjected to a Pin-on-Disc wear testing.The coated samples have shown almost negligible wear loss as compared to the uncoated samples. Further sliding wear resistance of is almost double of that of coated samples.

Characterization Of Cerment Composite Coating Al2O3-Ni System

This paper report on the possibility used new technique method by thermal spray coating to produce ceramic-metal coating of nano Al2O3-30%Wt. Ni samples. In this process nano crystalline cermet powders with grain size below 50nm were obtained by mechanical alloying. The steel substrates were degreased and grit blasted with SiC particles to get a mean roughness of 5µm. Experimentally the coating used under the best spraying parameters were deposited on steel substrate with thickness around 1.85mm. This powder and thick coating layers have been characterized by using XRD, SEM, EdS and hardness techniques. The X-ray results show that cerment coating consists a lot of phases such as ɤ-Ni, α-Al2O3 and ɤ-Al2O3 phases. The results also found that the wear resistance is superior, under high load conditions. The improved wear is attributed to the higher values of hardness. Results also show that Nickel was attractive for achieving good self-bonding with ceramic Al2O3 particles for all cerment samples.

Tribological performance of Yttrium (III) and Zirconium (IV) ceramics reinforced WC–10Co4Cr cermet powder HVOF thermally sprayed on X2CrNiMo-17-12-2 steel

In this paper, an experimental study has been performed on failure analysis of cermet coatings thermally sprayed on X2CrNiMo-17-12-2 stainless steel using a high-velocity oxy-fuel (HVOF) technique. A comparative study was carried out to investigate the microstructural, mechanical and tribological properties of pure and ceramic-reinforced WC–10Co4Cr cermet coatings. Two different feedstocks i.e. Yttrium-III (Yttria) and Zirconium-IV (Zirconia) were used to develop two different ceramic-reinforced WC–10Co4Cr powders. Tribological properties were tested with the help of laboratory scale pot tester. Coal ashes (i.e., fly ash and bottom ash) were used as the erodents. Different parameters like velocity, time, concentration of particles, and impact angle were varied during the tribological experiments. The microstructural analysis reveals the interlocked lamellae splats, pores and unmelted particles on the as-sprayed surfaces. Yttria reinforced WC–10Co4Cr coating exhibit superior tribo-resistance and mechanical properties. The zirconia reinforced WC–10Co4Cr coating has shown good wear resistance in fly ash slurry which possesses a weak acidic nature (pH = 6.32–6.09 for concentration range of 30–60 wt%). Microhardness of WC–10Co4Cr cermet was also improved with the addition of Yttria. The erosion mechanisms were analyzed by using backscattered X-ray scanning electron microscope (SEM), interactive 3D surface plots, and 2D pseudo-images.

Preparation of Ti(C, N)-based Cermets Powders with Double-core Ring Structure

In this study, the microstructure of Ti(C, N)-based cermet was improved by adding β-cobalt (face-centered cubic) and (Ti, W, Mo, Ta)(C, N) solid solution powder to prepare micro-nano Ti(C, N)-based cermet powder. In order to improve the comprehensive properties of the material. Firstly, the Co powder with face-centered cubic structure was obtained by the solid-phase reaction of high-energy ball milling, and its plastic deformation resistance was higher than that of Co powder with dense hexagonal structure. Secondly, The powder of (Ti, W, Mo, Ta)(C, N)solid solution was obtained by mechanical alloying and high-temperature carbonization under the atmosphere of N2. And the two were applied to the micro-nano Ti(C, N)-based cermet powder, and finally the properties of cermet powder were compared with that of ordinary cermet powder. The results show that the microstructure of micro-Ti(C, N)-based cermet powder prepared in this study is a double-core rim structure, that is, the structure of black core white rim and gray core white rim. This structure can effectively prevent crack of the expansion. The strength and toughness of cermet materials are greatly improved, which is beneficial to the improvement of comprehensive properties of cermet materials.

Considerations regarding WC-cermets depositions by HVOF and ESD techniques used for reinforced steel components for geothermal turbines

The cumulative effect of erosion-corrosion process in geothermal turbines results in significant damages, especially for rotors and turbine blades; the degree in which they are affected depends on steam temperature, mechanical impact and the geothermal composition of the substances dissolved in steam. Layer composite materials are a feasible option to improve the erosion-corrosion resistance and the durability of turbine components. There cermet powders containing tungsten carbide are used for High Velocity Oxy-Fuel (HVOF) spaying and for Electro Spark Deposition (ESD) to obtain graduate microstructure and to form local hard structures. Both techniques by WC-cermet depositions were found to be most suitable to improve wear resistance, to repair rotors and blades and to provide possible life extension of geothermal turbines. The paper presents a comparative assessment of tungsten carbide and the technological parameters used for HVOF and ESD cermets layers depositions. Also, the work presents the analysis of the micro chemical composition of the microstructure, the micromechanical characterization and erosion-oxidation resistance of HVOF and ESD coatings using WC-cermets on steel substrates. The experimental procedure involved X-ray diffraction of the samples, micro mechanical tests and SEM investigations to provide specifically information about micro-morphological modifications and grade of adhesion of protective layers.

Effect of the Microstructure of Cermet Powders on the Performance Characteristics of Thermal Spray Coatings

Comparative analysis of the performance characteristics of thermal spray coatings, in particular, detonation coatings formed from commercial tungsten-carbide-based WC−Со (12 wt %) powder (1342VM, Praxair, United States) and cermet TiC−Ме (19 vol %) powder (Ме = NiCr, Co) obtained by self-propagating high-temperature synthesis followed by spheroidization in a plasma jet is performed. It is shown that carbide particles of the cermet powder with a size of greater than 3 µm have structural defects in the form of cracks and pores. Their appearance is explained phenomenologically. It is established that spheroidized particles inherit the internal microstructure. They are dense, whereas the porosity of tungsten carbide based WC−Со (12 wt %) particles attains 40%. The effect of the density of particles on the powder-deposition efficiency and the porosity of coatings is revealed. When a dense powder is sprayed, its deposition efficiency is decreased from 54 to 33%, and the porosity of coatings increases from 0.4 to 1.78%. The WC−Со (19 vol %) coating has the best wear resistance due to the splinter shape of carbide particles with a size of nearly 1 µm.

Effects of Mechanical Ball Milling Time on the Microstructure and Mechanical Properties of Mo2NiB2-Ni Cermets.

Mo2NiB2-Ni cermets have been extensively investigated due to their outstanding properties. However, studies have not systematically examined the effect of the powder milling process on the cermets. In this study, Mo, Ni, and B raw powders were subjected to mechanical ball milling from 1 h to 15 h. XRD patterns of the milled powders confirmed that a new phase was not observed at milling times of 1 h to 15 h. With the increase in the mechanical ball milling time from 1 h to 11 h, raw powders were crushed to small fragments, in addition to a more uniform distribution, and with the increase in the mechanical ball milling time to greater than 11 h, milled powders changed slightly. Mo2NiB2-Ni cermets were fabricated by reaction boronizing sintering using the milled powders at different ball milling times. The milling time significantly affected the microstructure and mechanical properties of Mo2NiB2-Ni cermets. Moreover, the Mo2NiB2 cermet powder subjected to a milling time of 11 h exhibited the finest crystal size and the maximum volume fraction of the Mo2NiB2 hard phase. Furthermore, the cermets with a milling time of 11 h exhibited a maximum hardness and bending strength of 87.6 HRA and 1367.3 MPa, respectively.