Co-based Composite Coatings Research Articles

Investigation of the microstructure and tribological properties of laser cladding 5%Ti3SiC2 reinforced Co-based composite coatings under different loads over the wide temperature range

In order to improve the mechanical properties of SUS 304 in practical engineering application, Co-5%Ti3SiC2 coating was successfully prepared on SUS 304 by laser technology. The microstructure of Co-5%Ti3SiC2 coating was characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD) to evaluate the tribological properties in detail. The relevant wear mechanism of the substrate and Co-5%Ti3SiC2 coating under different loads (2, 5 and 8 N) in isothermal tribological experiments (25 and 600 °C) were systematically explored. The results show that the Co-5%Ti3SiC2 coating is mainly composed of continuous matrix γ-Co solid solution, ceramic Fe2C, Cr7C3 and TiC, and lubricating phase Ti3SiC2. The average micro-hardness of Co-5%Ti3SiC2 coating is 358.61 HV0.5, which is significantly higher than that of SUS 304 (239.32 HV0.5). In all isothermal tribological experiments, the wear rate of Co-5%Ti3SiC2 coating decreases with the increase of load, and its coefficient of friction (COF) also decreases with the increase of load.

Facile construction of CeO2@MoS2 nanohybrid for enhancing tribological performance of electroplated Co-based composite coatings

Developing and manufacturing novel coatings with excellent tribological performance using environmentally friendly and simple methods hold significant potential and challenge for reducing energy consumption and carbon emissions. Here, we use a gentle method to synthesize the MoS2-load CeO2 nanohybrid (CeO2@MoS2) as an additive to construct a Co-CeO2@MoS2 composite coating with friction reduction and wear resistance through a low-cost electrodeposition technique. The friction measurement results show that CeO2@MoS2 nanohybrid effectively reduces the friction coefficient and increases the wear resistance compared to single CeO2 or MoS2. The synergistic effect of hard CeO2 and soft MoS2 gives the Co-CeO2@MoS2 coating with an extremely low coefficient of friction of about 0.05 and a wear rate of about 3.53×10−6 mm3(N·mm)−1. In addition, the Co-CeO2@MoS2 coating can maintain an extremely low coefficient of friction with long-term stability in tribological tests. This work provides a novel strategy for constructing coatings with remarkable tribological performances and promotes the application of CeO2@MoS2 nanohybrid as an additive to improve material properties.

Design, Manufacturing, Microstructure, and Surface Properties of Brazed Co-Based Composite Coatings Reinforced with Tungsten Carbide Particles

Brazing is a joining process that involves melting a filler metal and flowing it into the joint between two closely fitting parts. While brazing is primarily used for joining metals, it can also be adapted for certain coating deposition applications. The present study investigates the microstructure and corrosion behavior and sliding wear resistance of WC (Tungsten Carbide)-CoCr-Ni reinforced Co-based composite coatings deposited onto the surface of AISI 904L stainless steel using a vacuum brazing method. The primary objective of this experimental work was to evaluate the influence of WC-based particles added to the microstructure and the properties of the brazed Co composite coating. The focus was on enhancing the sliding wear resistance of the coatings while ensuring that their corrosion resistance in chloride media was not adversely affected. The morphology and microstructure of the composite coatings were investigated using scanning electron microscopy (SEM) and phase identification by X-ray diffraction (XRD). The SEM analysis revealed in the coating the presence of intermetallic compounds and carbides, which increase the hardness of the material. The sliding wear resistance was assessed using the pin-on-disk method, and the corrosion properties were determined using electrochemical measurements. The results obtained showed that as the WC particle ratio in the Co-based composite coating increased, the mechanical properties improved, the alloy became harder, and the tribological properties were improved. The evaluation of the electrochemical tests revealed no significant alterations of the manufactured composite in comparison with the Co-based alloys. In all cases, the corrosion behavior was better compared with that of the stainless-steel substrate.

Fabrication and tribological properties of laser cladding WC-Cu/Co-based composite coatings

Different proportions of WC/Cu particle-reinforced Co-based composite coatings were successfully prepared by laser cladding on the Inconel 718 superalloy to investigate their tribological properties sliding against the Si3N4 ball at room temperature (RT) and 600 °C. The results show that the addition of WC and Cu can serve to improve the microhardness and tribological properties of the composite coatings. The composite coatings demonstrated a greater than 1.7-fold increase in microhardness as compared to the substrate, which was mainly attributed to the grain refinement of the coatings resulting from the γ-Co phase and intergranular eutectic structure, and the presence of hard phases, such as WC, FexNby and Cr2C3. Notably, the 5wt.%WC and 5wt.%Cu additives obviously raise the wear resistance of Co-based composite coating, in which significant decreases in wear rates are attained under RT (∼84.4 %) and 600 °C (∼64.9 %). In addition, excellent friction-reduction abilities are also found in the Co-5wt.%WC-10wt.%Cu coating at RT and Co-5wt.%WC-15wt.%Cu coating at 600 °C, with corresponding friction reductions of about 30.8 % and 26.7 %, respectively. The main wear mechanisms of coatings were found to be oxidative and fatigue wear at RT; oxidative and adhesive wear at 600 °C.

Research Status and Analysis of Co-Based Composite Coatings Prepared by Laser Cladding

Research Status and Analysis of Co-Based Composite Coatings Prepared by Laser Cladding

Microstructure and properties of graphene reinforced co-based composite coating by laser cladding

Graphene (Gr)-reinforced Co-based (Co50) composite coatings were prepared on 40Cr steel substrates by laser cladding technology. The effects of different amounts of Gr addition on the microstructure and mechanical properties of the coating were studied. The addition of a proper amount of Gr can improve the comprehensive properties of the coating, and most of the Gr forms carbides, such as Cr23C6 and Cr7C3, under the action of laser irradiation. The addition of Gr can significantly refine the grains and evenly distribute them. When the addition of Gr is 3 wt%, the average grain size in the coating is the smallest, which is 5.7 μm, and the highest microhardness reaches 777.5 HV0.2, which is an increase of 270.2 % compared with that of the substrate. The unmelted Gr remains dispersed in the coating, which can improve lubrication and reduce friction. The average friction coefficient and wear volume are decreased to 0.335 and 4.26 × 107 μm3, which are approximately 54.2 % and 28.0 % of those of the substrate, respectively.

Evaluation of wear and corrosion resistances of laser cladding TaC/TiC/Stellite X-40 Co-based composite coatings on copper surface

ABSTRACT The TaC/TiC/Stellite X-40 Co-based composite coatings with different contents were successfully cladded on a Cr-Zr-Cu alloy substrate. The microstructure, wear and corrosion resistance of the composite coatings were investigated by means of X-ray diffraction (XRD), optical microscope (OM), energy dispersive spectrometer (EDS), scanning electron microscope (SEM), sliding wear test, as well as corrosion test in 3.5% NaCl solution. The results showed that Ta and Ti atoms easily form Co3Ta and Co3Ti hard phases with Co to increasing the hardness of the coating. Compared with the substrate, the wear resistance, corrosion resistance and hardness of the composite coatings were significantly improved. The wear resistance of the 20 wt. % TaC and 10 wt. % TiC composite coatings were better than that of the substrate. When the TaC content was 20 wt. % and the TiC content was 15 wt. %, the coating with excellent corrosion resistance (-0.153V).

Improving surface resistance to wear and corrosion of nickel‑aluminum bronze by laser-clad TaC/Co-based alloy composite coatings

TaC/Stellite X-40 Co-based composite coatings were fabricated on nickel‑aluminum bronze (NAB) substrates by laser surface cladding (LSC), aiming at improving wear and corrosion resistances of NAB in marine environments. The morphology, microstructure, microhardness, wear and electrochemical corrosion behaviors of the surface treated composite coatings were studied. The results showed uniform distribution of carbide and intermetallic reinforcements such as TaC, Cr3C2 and Co3Ta in γ-Co matrix which lead to improvements of resistances to wear and electrochemical corrosion. Microstructural analyses of the LSC coating containing 20 wt% TaC showed the presence of fine reinforcements with isocellular crystals in the surface region and refined columnar crystal near the substrate area, as well as metallurgical bonding between the LSC coating and the NAB substrate. With the increase of TaC content in the cladding powders, the number of the granular reinforcements in the LSC coatings increased gradually, and the particles became larger. The maximum average microhardness of the composite coating of 20 wt% TaC was about 771.7 HV0.2, which is approximate 6.2 times higher than that of the NAB substrate (125.1 HV0.2). The minimum average coefficient of friction (COF) of the composite coatings was about 0.303 and its wear rate was about 0.4 times that of the NAB substrate. The self-corrosion potential (−0.182) of the composite coating with 20 wt% TaC was significantly higher than that of the substrate (−0.298), and the current density was lower, which implies that the corrosion resistance of the coating was significantly improved.

Microstructure and tribological properties of in-situ synthesized TiC reinforced reactive plasma sprayed Co-based coatings

In this study, TiC in-situ reinforced Co-based composite coatings (Co–TiC) were fabricated by reactive plasma spraying using Ti-graphite and Co-based alloy powders. The microstructure, mechanical and tribological properties were investigated. The hardness and tribological properties were measured by Vickers indenter and circular sliding tester. Si3N4 was used as friction counterpart, the sliding speed was 400r/min, the normal load was 30 N, and the sliding time was 30min. The results showed that Co–TiC coatings consisted of TiC, α-Co, Fe3Ni3B, Ni31Si12 and TiO2 phases. TiC phase was formed by the reaction between Ti and C directly. With the increase of Ti-graphite powders addition, more TiC was synthesized in-situ. The in-situ formed TiC enhanced the hardness and wear resistance of the coatings, coupling with forming small porosities (<9%). The highest hardness was 1035HV0.2 for Co–15TiC, which is about 20% higher than that of Co coating. The lowest wear volume was 0.0745 mm3 for Co–15TiC coating, which is just 13% of that of Co coating. The main wear mechanism of Co–TiC coatings in the present sliding test was abrasive wear.

Microstructure and Property of In-Situ TiC Reinforced Co-Based Composite Coatings by Laser Cladding

In order to improve the wear resistance of Co-based alloy coatings, in-situ TiC reinforced Co-based composite coatings were prepared on 45 steel surface by laser cladding Co-based alloy, Ti and C powders. The effect of (Ti + C) addition on the microstructure and wear resistance of in-situ TiC reinforced Co-based composite coatings was investigated systematically. The results showed that TiC and Co3Ti phases were detected in the in-situ TiC reinforced Co-based composite coatings, besides γ-Co and Cr23C6. The in-situ TiC reinforced Co-based composite coatings was mainly composed of planar crystals in the binding zone, dendrites in the bottom and equiaxed crystals in the upper. With the increase of (Ti + C) addition, the number of short rod-like dendrites and equiaxed crystals was gradually increased, the microstructure was more fine and uniform. The microhardness of the composite coatings was improved gradually, and the maximum improvement in the microhardness was 35.7%, for 30.0 wt.% (Ti + C) addition. The mass loss of the composite coatings was firstly reduced and then increased, the lowest value was 10.5 mg for 20.0 wt.% (Ti + C) addition, which was 59.7% of that of Co-based alloy coatings, and the wear mechanism of the composite coatings after adding (Ti + C) was the abrasive wear. These results indicated that adding (Ti + C) had a significant influence on the properties of the composite coatings, and were consistent with the calculated results of applied multivariate statistical analysis.

In-situ SEM observations of ultrasonic cavitation erosion behavior of HVOF-sprayed coatings.

Several typical high-velocity oxy-fuel (HVOF)-sprayed coatings, including WC-10Co4Cr coatings, Co-based coatings, WC-10Co4Cr/Co-based composite coatings, and Fe-based amorphous/nanocrystalline coatings were fabricated, and their cavitation behavior was evaluated in deionized water. Further, in-situ SEM surface observations were used to understand the microstructure of tested coatings. The results show that cavitation erosion initially occurred at pre-existing defects in the coatings. Meanwhile, it was found that cavitation erosion damage of the WC-10Co4Cr/Co-based composite coating, which contained a hard reinforcing phase (WC-10Co4Cr phase) and a soft matrix phase (Co-based phase), preferentially occurred at or around pores and microcracks in the reinforcement, rather than in the defect free matrix. This suggested that defects were a critical contributing factor to cavitation damage of the composite coatings. Furthermore, a mechanism was suggested to explicate the cavitation behavior of composite coatings. The approach of using in-situ SEM surface observations proved to be useful for the analysis of the cavitation mechanism of engineering materials and protective coatings.

A Comparative Study of Cavitation Erosion Resistance of Several HVOF-Sprayed Coatings in Deionized Water and Artificial Seawater

In this study, WC-10Co4Cr coatings, Co-based coatings, WC-10Co4Cr/Co-based composite coatings, and Fe-based amorphous/nanocrystalline coatings were prepared on 316L stainless steel substrates by a high-velocity oxy-fuel spraying process. The cavitation erosion resistances of all the coatings, as well as the stainless steel substrates, were investigated in deionized water and artificial seawater. Results show that the effect of marine corrosion on cavitation erosion was most significant on the stainless steels, WC-10Co4Cr coatings, and Co-based coatings, but negligible on the WC-10Co4Cr/Co-based composite coatings and the Fe-based amorphous/nanocrystalline coatings. The WC-10Co4Cr coatings (0.17 mm3/h) show improved cavitation erosion resistance than those of WC-10Co4Cr/Co-based composite coatings (0.21 mm3/h), 316L stainless steel substrates (0.22 mm3/h), Co-based coatings (0.30 mm3/h), and Fe-based coatings (0.47 mm3/h) in marine environments.

Elevated Temperature Solid Particle Erosion Performance of Plasma-Sprayed Co-based Composite Coatings with Additions of Al2O3 and CeO2

In this paper, investigation into solid particle erosion behavior of atmospheric plasma-sprayed composite coating of CoCrAlY reinforced with Al2O3 and CeO2 oxides on Superni 76 at elevated temperature of 600 °C is presented. Alumina particles are used as erodent at two impact angles of 30° and 90°. The microstructure, porosity, hardness, toughness and adhesion properties of the as-sprayed coatings are studied. The effects of temperature and phase transformation in the coatings during erosion process are analyzed using XRD and EDS techniques. Optical profilometer is used for accurate elucidation of erosion volume loss. CoCrAlY/CeO2 coating showed better erosion resistance with a volume loss of about 50% of what was observed in case of CoCrAlY/Al2O3/YSZ coating. Lower erosion loss is observed at 90° as compared to 30° impact angle. The erosion mechanism evaluated using SEM micrograph revealed that the coatings experienced ductile fracture exhibiting severe deformation with unusual oxide cracks. Reinforced metal oxides provide shielding effect for erodent impact, enabling better erosion resistance. The oxidation of the coating due to high-temperature exposure reforms erosion process into oxidation-modified erosion process.

Effect of aging treatment on microstructure and properties of VN alloy reinforced Co-based composite coatings by laser cladding

Laser cladding VN alloy reinforced Co-based composite coatings on the mild steel was aging treated at 550°C, 650°C and 750°C, respectively. Effects of aging temperature on the phase compositions, microstructure, microhardness, and wear resistance of the composite coatings with and without heat treatment had been investigated systemically. The results showed phase compositions of the composite coatings were not affected after aging treatment at 550°C and 650°C, and σ-FeV phase was not detected after aging treatment at 750°C. The volume fraction of Cr23C6 and VN was gradually increased with the increasing of aging temperature. The number of short rod-shaped dendrites and equiaxed grains in the composite coatings was gradually increased as aging temperature increased, the distribution of the equiaxial grains was more uniform, and the dislocation density was reduced. Compared with the composite coatings without aging treatment, the microhardness and wear resistance of the composite coatings were both firstly decreased after aging treatment at 550°C and 650°C, then gradually increased with the increase of aging temperature, and the increase was 9.9% and 10.7%, respectively, for aging treatment at 750°C. The wear mechanism of three composite coatings were all the abrasive wear.

Microstructure and wear property of the Ti5Si3/TiC reinforced Co-based coatings fabricated by laser cladding on Ti-6Al-4V

Ti5Si3/TiC reinforced Co-based composite coatings were fabricated on Ti-6Al-4V titanium alloy by laser cladding with Co42 and SiC mixture. Microstructure and wear property of the cladding coatings with different content of SiC were investigated. During the cladding process, the original SiC dissolved and reacted with Ti forming Ti5Si3 and TiC. The complex in situ formed phases were found beneficial to the improvement of the coating property. Results indicated that the microhardness of the composite coatings was enhanced to over 3 times the substrate. The wear resistance of the coatings also showed distinct improvement (18.4–57.4 times). More SiC gave rise to better wear resistance within certain limits. However, too much SiC (20wt%) was not good for the further improvement of the wear property.

Effect of process parameters on the microstructure evolution and wear property of the laser cladding coatings on Ti-6Al-4V alloy

In this paper, Co-based composite coatings were fabricated by laser cladding Co42 + B4C mixed powders on Ti-6Al-4V titanium alloy. The comprehensive effects of laser power and scanning velocity on the microstructure evolution and wear property of the laser cladding coatings were studied. Results indicated that the coatings were mainly comprised of γ-Co/Ni, TiC, TiB2, TiB, NiTi, CoTi, CoTi2, and Cr7C3. With the decreasing of laser specific energy (from 12.7 kJ cm−2 to 4.9 kJ cm−2), the TiC dendrites and TiB particles were refined. Compared with the Ti-6Al-4V titanium alloy, the microhardness and wear resistance of the composite coatings were enhanced obviously. Lower laser specific energy led to higher microhardness and better wear resistance owing to more TiB2 bulks distributed in the cladding coating.

WC Particles Reinforced Co-Based Alloy Coatings Produced by Laser Cladding

To extend the service life of hot die steel (H13), WC particles reinforced Co-based alloy composite coatings were produced by laser cladding. The microstructure evolution and performance of the cladding layer were investigated. The experiment results showed that there existed fine dendritic crystals and dispersive WC particles in the cladding layer. The coatings were mainly composed of γ-Co, WC and Co3W3C phases. The microhardness of the cladding layer was higher than that of the arc surfacing layer, and the microhardness gradually increased with WC content. Compared to the substrate, the friction coefficient of the cladding layer reduced greatly. The coatings with 15wt.% WC possess the best wear resistance.

Microstructures and properties of TiN reinforced Co-based composite coatings modified with Y2O3 by laser cladding on Ti–6Al–4V alloy

In this study, TiN reinforced composite coatings were fabricated on Ti–6Al–4V substrate by laser cladding with Co42 self-fluxing alloy, TiN and Y2O3 mixed powders. Microstructures and wear resistance of the cladding coatings with and without Y2O3 addition were investigated comparatively. Results showed that the coatings were mainly comprised of γ-Co/Ni, TiN, CoTi, CoTi2, NiTi, TiC, Cr7C3, TiB, Ti5Si3 and TiC0.3N0.7 phases. The coatings showed metallurgical bonding free of pores and cracks with the substrate. Compared with the Ti–6Al–4V substrate, the microhardness and wear resistance of the coatings was enhanced by 3–4 times and 9.5–11.9 times, respectively. With 1.0 wt.% Y2O3 addition, the microstructure of the coating was refined significantly, and the microhardness and dry sliding wear resistance were enhanced further. The effects of Y2O3 were attributed to the residual Y2O3 and decomposed Y atoms.

Effect of nano-CeO2 on microstructure and wear resistance of Co-based coatings

Co-based composite coatings with different nano-CeO2 contents were successfully prepared on SPHC steel by laser cladding. The effect of nano-CeO2 on microstructure and properties of Co-based coatings were systematically investigated. The phase construction and microstructure of the coatings were characterized by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectrometer (EDS). The hardness and wear resistance of the coatings were evaluated by HV-1000 hardness tester and MM-200 type wear tester at room temperature as well as applied multivariate statistical analysis method. The results indicated that Co-based coatings with nano-CeO2 exhibited an excellent appearance quality, another fine microstructure and new phase Ce2Ni7 appeared. The microhardness and wear resistance of coatings first improved and then decreased with increasing nano-CeO2 content in the coatings and the improvement in microhardness and the reduction in total loss were respectively 35.3% and 55.0%, at 1.5wt.% nano-CeO2, the wear mechanism was abrasive wear. The great effect of nano-CeO2 addition on microhardness and wear resistance of coatings were consistent with the calculation results of applied multivariate statistical analysis. Thus, it is concluded that adding nano-CeO2 is an effective and attainable way to improve the wear resistance of Co-based coatings.

Microstructures and wear properties of laser cladding Co-based composite coatings on Ti–6Al–4V

Abstract Metal matrix composite (MMC) coatings were fabricated on Ti–6Al–4V titanium alloy by laser cladding. Co42 self-fluxing powder, B 4 C, SiC and Y 2 O 3 were employed as the cladding materials. Microstructures and the wear properties of the different composite coatings were investigated comparatively. Results showed that the laser cladding coatings were mainly reinforced by CoTi, CoTi 2 , NiTi, TiC, TiB 2 , TiB, Cr 7 C 3 and Ti 5 Si 3 . The micro-hardness of the cladding coatings were equivalent to 3–4 times the Ti–6Al–4V substrate. Laser cladding coating exhibiting outstanding wear resistance was fabricated with the addition of 20 wt.% B 4 C, 7 wt.% SiC and 1 wt.% Y 2 O 3 . The wear resistance was enhanced by over 10 times compared with the substrate. However, with more SiC addition (14 wt.%), a higher micro-hardness was obtained together with poor wear resistance. The wear mechanism of the coatings was discussed by referring to the microstructures and the wear morphologies.