Corrosion Resistance to Molten Zinc of a Novel Cermet Coating Deposited by Activated Combustion High-Velocity Air Fuel (AC-HVAF)

Xie, Xu; Yin, Fei; Wang, Xinming; Ouyang, Xuemei; Li, Minghuan; Hu, Jing

doi:10.1007/s11666-019-00893-x

Cited by 12 publications

(2 citation statements)

References 36 publications

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“…Among high-temperature coatings that both resist oxidation and wear, cermet coating is composed of a metal bond phase and ceramic reinforcing phase, which is a kind of hightemperature protective coating with potential applications. It has the advantages of high bonding strength, superior toughness, good thermal shock resistance, good wear resistance, and good chemical stability [3,[5][6][7][8][9]. Especially, MCrAlY (M=Co, Ni, or Co + Ni) has good oxidation resistance, hot corrosion resistance, and thermal fatigue properties, and is widely used as the binder in cermet coatings, however, its wear resistance is poor [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

High-Temperature Oxidation Behavior of Plasma-Sprayed CoCrAlTaY-30Al2O3 Cermet Coating at 1050 °C

2022

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Cermet coatings with ceramic and metal characteristics will play an increasingly important role in extending the service life of critical components in harsh service environments. In this paper, CoCrAlTaY-30Al2O3 (wt.%) cermet coating was prepared by air plasma spraying technique. The effect of powder feeding rate on the microstructure and mechanical properties of the coating and its high-temperature oxidation behavior was investigated. The results showed that the CoCrAlTaY-30Al2O3 spraying powder mainly consisted of Al5Co2, α-Al2O3, Co, Cr7C3, and TaC in five phases. The microstructure of cermet coating was uniform and its porosity was relatively low. The coating was mainly composed of Al5Co2, Cr, and Al2O3 phases, and the change of powder feeding rate had no obvious effect on the phase composition of the coating. When the powder feeding rate was 32 g/min, the minimum porosity of the coating was (3.68 ± 0.86)%, and the maximum Vickers hardness and binding strength were (664.9 ± 55.9) HV0.3 and (78.6 ± 6.6) MPa, respectively. The oxidation rate constant kp1 of the coating at 1050 °C was 0.066 mg2∙cm−4∙h−1, and the fitted curve R2 value was 0.99547. In the oxidization initial stages, the alloy elements Co, Al, and Cr in the cermet coating were rapidly oxidized to form CoO, Al2O3, and Cr2O3. Then Al2O3 and Cr2O3 reacted with CoO to form Co(Al,Cr)2O4 spinel oxides. The θ-Al2O3 phase was formed after initial oxidation while the θ-Al2O3 phase was completely transformed into α-Al2O3 after 200 h. The oxide film mainly contained Co(Cr,Al)2O4, Cr2O3, and α-Al2O3 phases.

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Section: Introductionmentioning

confidence: 99%

High-Temperature Oxidation Behavior of Plasma-Sprayed CoCrAlTaY-30Al2O3 Cermet Coating at 1050 °C

2022

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“…This avoids substrate distortion and microstructural changes of the coating and substrate material. Activated combustion high-velocity air fuel (AC-HVAF) is a similar spray technique to HVOF but better coating density and lower oxide content can be achieved with AC-HVAF [136]. Plasma coating are applied in a similar way to the HVOF and AC-HVAF coatings where the coating material is in the form of a powder is injected into a high temperature flame where it is heated and accelerated to a high velocity.…”

Section: Coating Methodsmentioning

confidence: 99%

The Effects of Composition and Heat Treatment on the Microstructure and Performance of Cobalt-based Alloys for Molten Zinc Applications

Escott¹

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The purpose of this research was to identify and develop cobalt-based superalloys for journal bearing applications by improving the stability and service life of submerged galvanising pot hardware. To achieve this goal the mechanical properties and chemical resistance of four cast cobalt superalloys were investigated. The alloys were subjected to three heat treatments which included a high temperature annealing treatment, a solution treatment and additional age hardening, and a plasma nitriding treatment. The heat-treated alloys were examined and compared to untreated samples to identify any microstructural changes or improvements in material performance. Four commercially available cobalt-based superalloys were identified for analysis including three cast CoCrW alloys and one cast CoCrMo Tribaloy. It was identified that increasing the carbon and tungsten content, with the CoCrW alloys, increased the area fraction of chromium and tungsten carbide phases in addition to increasing the concentration of alloying elements retained in solid solution. Both factors contributed to increased material hardness. The substitution of tungsten with molybdenum and the absence of carbon, with the CoCrMo Tribaloy, replaced the formation of eutectic carbides with a primary Laves phase that dominated the Tribaloys microstructure. This provided the CoCrMo alloy with enhanced hardness properties compared to the CoCrW alloys. The untreated alloys were submerged in a molten zinc alloy bath containing 0.35wt.% Al in a series of static immersion tests where the alloys were submerged for times ranging between 1-4 weeks. All the materials reacted with the molten zinc bath resulting in the diffusion of bath species into the alloys microstructure as well as the leaching of alloying elements into the bath. With each alloy, molten metal ingress preferentially occurred in the cobalt rich solid solution phase whereas the carbide and Laves phases were more resistant to bath reactivity. The high area fraction of Laves phase and increased molybdenum concentrations retained in eutectic solid solution with the T-800 Tribaloy, provided the alloy with enhanced chemical resistance to the bath in comparison to the CoCrW alloys. The improved chemical resistance reduced the depth of diffusion and reduced the quantity of cobalt-aluminide formation at the alloys surface. A plasma nitriding treatment resulted in the formation of a nitrogen rich diffusion layer at the surface of each of the alloys. Increasing the treatment temperature or treatment time produced a thicker diffusion layer with increased concentrations of nitrogen. The formation a nitride layer significantly improved the surface hardness of each of the alloys where increased material hardness correlated with a thicker diffusion layer. The plasma treated samples were dip tested in a molten zinc bath containing 0.35wt.% Al. The formation of the nitride diffusion layer improved the long-term chemical performance of the alloys where reduced zinc and aluminium diffusion depths were recorded with the CoCrW alloys after 4-weeks of testing. The nitride treatment generally improved the surface integrity of the alloys where increased levels of alloying elements were retained within the matrix diffusion layer after prolonged bath exposure and each alloy experienced less material loss. There was also a noticeable reduction in the quantity of cobalt-aluminide phases at the alloy’s surfaces. An annealing heat treatment slightly changed the morphology of the alloy’s microstructure where phase precipitation within the solid solution phase occurred in addition to low levels of carbide dissolution. Small improvements in material hardness were recorded with the CoCrW alloys whereas the annealing treatment had detrimental effects on the hardness properties of the CoCrMo alloy. Using the nano-properties of the matrix to calculate the mean H/E ratio it was predicted that the wear performance of the matrix of the WT-4 and WT-12 alloys were slightly improved by the annealing process. A solution treatment significantly changed the microstructure morphology of the WT-6 and WT-12 alloys. The solution treatment resulted in extreme coarsening of the chromium and tungsten carbides with the WT-12 alloy and coarsening of the chromium carbides and the precipitation of tungsten rich phases with the WT-6 alloy. Low levels of carbide dissolution were also recorded. A drop in material hardness was recorded with both alloys after the solution treatment. Additional aging treatments did not significantly alter the alloys microstructures further but precipitation within the matrix occurred. This coincided with significant improvements in the hardness properties of both alloys. Calculating the mean H/E ratio of the matrix phase in both alloys estimated that no improvements in matrix wear resistance occurred with WT-6 alloy whereas an improvement with the WT-12 matrix was calculated.

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Corrosion Resistance to Molten Zinc of a Novel FeB-10 Mo-12 Al0.25FeNiCoCr Cermet and Coating

et al. 2022

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Corrosion Resistance to Molten Zinc of a Novel Cermet Coating Deposited by Activated Combustion High-Velocity Air Fuel (AC-HVAF)

Cited by 12 publications

References 36 publications

High-Temperature Oxidation Behavior of Plasma-Sprayed CoCrAlTaY-30Al2O3 Cermet Coating at 1050 °C

High-Temperature Oxidation Behavior of Plasma-Sprayed CoCrAlTaY-30Al2O3 Cermet Coating at 1050 °C

The Effects of Composition and Heat Treatment on the Microstructure and Performance of Cobalt-based Alloys for Molten Zinc Applications

Corrosion Resistance to Molten Zinc of a Novel FeB-10 Mo-12 Al0.25FeNiCoCr Cermet and Coating

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