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This paper aims to discuss that a WC/Co-Cr alloy coating was applied to the surface of H13 steel by laser cladding.

The oxidation behavior of the WC/Co-Cr alloy coating at 600°C was investigated by comparing it with the performance of the steel substrate to better understand the thermal stability of H13 steel.

The results showed that the WC/Co-Cr alloy coating exhibited better high-temperature oxidation resistance and thermal stability than did uncoated H13 steel. The coated H13 steel had a lower mass gain rate and higher microhardness than did the substrate after different oxidation times.

The WC/Co-Cr alloy coating was composed of e-Co, CW3, Co6W6C, Cr23C6 and Cr7C3; this mixture offered good thermal stability and better high-temperature oxidation resistance.

This paper aims to investigate the hot corrosion behavior of Ni-Cr and Cr3C2-NiCr coatings, deposited on T11, P91 boiler steels by detonation gun spray coating (D-Gun) process to enhance high temperature corrosion resistance.

Hot corrosion studies were conducted in secondary super heater zone of boiler at 900 °C for 10 cycles on bare and D-Gun coated steel specimens. The microhardness and porosity values of as-sprayed coatings were measured before exposing the specimens in the boiler environment. Each cycle consisted 100 h of heating in the boiler environment followed by 20 min of cooling in air. The weight change measurements were performed after each cycle to establish the kinetics of corrosion using thermogravimetric technique. X-ray diffraction, SEM techniques were used to analyze the corroded specimens.

Uncoated boiler steel experienced higher weight loss. The Cr3C2-NiCr coating was found to be more protective than Ni-Cr coating. The phases revealed the formation of oxide scale on coated specimens, mainly consist of nickel and chromium, which are reported to be protective against the hot corrosion.

There is very limited reported literature on hot corrosion behavior of Ni-Cr and Cr3C2-NiCr coatings deposited on the T11 and P91 substrates by detonation gun (D-gun) spray technique. T11 and P91 alloy steels have been chosen for this study because these two alloys are used to manufacture boiler tubes used in Indian thermal power plants.

This paper aims to discuss that a conventional Al₂O₃, 1.5 Wt.% carbon nanotubes (CNTs)-Al₂O₃, 2 Wt.% CNTs-Al₂O₃ and 4 Wt.% CNTs-Al₂O₃ composite coatings were deposited with the help of Plasma spray process.

To better understand the effect of CNT reinforcement on oxidation resistance, high-temperature oxidation behaviour of conventional Al₂O₃, 1.5 Wt.% CNTs-Al₂O₃, 2 Wt.% CNTs-Al₂O₃ and 4 Wt.% CNTs-Al₂O₃ composite coatings at 900°C was compared with the performance of the uncoated ASME-SA213-T11 boiler tube steel substrate.

The results showed that the CNT-reinforced alumina coatings exhibited better oxidation resistance and thermal stability than uncoated ASME-SA213-T11 boiler tube steel. The coated steel substrates had a lower mass gain rate than the substrate after different oxidation times.

Limited literature is available where the CNT have been reinforced into the composite alloy powders and has been thermally spray-deposited for various surface engineering applications. This research showed that with the increase in the percentage of CNTs into the alloy powder mixture, there is a significant reduction in weight gain and hence higher resistance to oxidation.

Due to the special service environment of superalloys, this paper aims to obtain effects of temperature and Ti addition on high temperature oxidation behavior of Co-Al-W-B alloys.

Isothermal oxidation experiment of Co-Al-W-based alloys were carried out at 800°C, 900°C and 1000°C for different times (3, 5, 10, 20, 50 and 100 h) referring to the method of HB5258-2000. Oxidation weight gain curves and oxidation products were detected.

The results showed that the average oxidation rates of Co-Al-W-B alloy at 800 °C and 900 °C were 0.489 g·m⁻²·h⁻¹ and 0.888 g·m⁻²·h⁻¹, respectively, which belonged to an antioxidant grade. However, the average oxidation rate at 1000 °C was 2.068 g m⁻²·h⁻¹, belonging to the secondary oxidation resistance class. In the alloy with Ti addition, dense Ti oxides film were formed at the early oxidation stage and then gradually diffused later, which can increase the oxidation resistance of the alloys to some extent. By analyzing the oxidation products of Co-Al-W-B alloy, it was found that a dense Al₂O₃ layer could be formed when the alloy was oxidized at 800°C. The continuous Al₂O₃ layer would prevent the oxygen from further spreading and make the alloy into the stable oxidation stage. However, only a non-dense Al₂O₃ layer were observed with 900°C oxidation.

It can provide references for the composition design, preparation process optimization and protective coating selection of the γ′ phase strengthened cobalt-base superalloys.

This paper seeks to summarise the results of available research on the use of high velocity oxy‐fuel (HVOF) thermal‐spray technique to provide protection against high temperature corrosion and erosion‐corrosion of materials.

This paper describes one of the recent thermal‐spray processes, namely HVOF thermal‐spray technology and presents a survey of the studies on the use of this technique to provide protection against corrosion and erosion‐corrosion of high temperature alloys, with a special emphasis on boiler steels.

High temperature corrosion and erosion‐corrosion are serious problems observed in steam‐powered electricity generation plants, gas turbines, internal combustion engines, fluidized bed combustors, industrial waste incinerators and recovery boilers in paper and pulp industries. These problems can be prevented by changing the material or altering the environment, or by separating the component surface from the environment. Corrosion prevention by the use of coatings for separating materials from the environment is gaining importance in surface engineering. Amongst various surface modifying techniques, thermal spraying has developed relatively rapidly due to the use of advanced coating formulations and improvements in coating application technology. One of the variants of thermal spraying, namely HVOF has gained popularity in recent times due to its flexibility for in‐situ applications and superior coating properties.

This review covers mainly information that has been reported previously in the open literature, international journals and some well‐known textbooks.

The paper presents a concise summary of information for scientists and academics, planning to start their research work in the area of surface engineering.

This paper fulfils an identified information/resources need and offers practical help to an individual starting out on a career in the area of surface engineering for erosion‐corrosion and wear.

The purpose of this technical paper is to investigate the friction and wear behavior of inexpensive and durable cutting tools, developed for wood machining using duplex treatment.

Cr–(WC–Co) coatings were deposited onto carburized low-alloy steel substrate by a reactive magnetron sputtering. The total coating thickness was approximately 2 μm. Unlubricated wear tests have been performed using a disc sample sliding against an alumina ball (Al₂O₃) and a wood (beech) pin.

The paper provides information about the effect of duplex treatment on the surface properties of low-alloy steel against wood and offers practical help for the researchers in coating topic.

Experimental results showed that sliding wear properties of the selected coatings are strongly dependent on the counter-face material. When tested against alumina balls, the wear mechanisms are oxidative wear followed by a combination of adhesive and abrasive wear, while a combination of an oxidative and adhesive wear was the main wear mechanism observed against a wood pin.

Four thermal spray coatings were subjected to high temperature corrosive environments of oil‐fired boiler conditions to compare their corrosion protection under simulated conditions. The coatings included FeCrAl, Tafaloy 45CT, which were arc‐sprayed, 50Ni‐50Cr and Cr₃C₂‐NiCr, which were coated by high velocity oxy fuel spray (HVOF) method.

The coating substrates used were SA213TP 347H, SA213 T11 and SA213 T22 alloys that are widely used as boiler tube materials. Specimens were covered with a synthetic ash mixture of 70 per cent V₂O₅‐20 per cent Na₂SO₄‐10 per cent NaCl and exposed to 550°C and 650^oC°for 192 h (6 cycles). After high temperature corrosion tests, weight change curves were obtained; specimens were examined by metallographical techniques, scanning electron microscopy and EDX analyses.

Salt deposits attacked steels and coatings during the exposure. The corrosion rates were strongly affected by the composition of the scale formed adjacent to the steels and coatings surfaces. Austenitic steel was only bare material that experienced uniform corrosion in the tests. Ferritic steels were primarily attacked by grain boundary corrosion. Thermally sprayed coatings were mainly attached through oxides and voids at splat boundaries. FeCrAl and 50Ni‐50Cr were prone to spalling. Tafaloy 45CT is also a promising method for producing homogenous coatings. Cr₃C₂‐NiCr 80/20 coating remained mostly intact.

This paper provides useful information about corrosion behaviours of four coatings used for common boiler tubes. It shows with a practical explanation how the bare material and coatings react in corrosion simulated environments.

This paper aims to investigate hot corrosion behaviour of different Cr₃C₂–NiCr coatings on boiler tube steel.

High velocity oxy fuel technique has been used to deposit different coatings on commercially available ASTM-SA213-T22 boiler tube steel. The hot corrosion studies have been performed in molten salt environment at 900°C temperature in silicon tube furnace in laboratory.

The results showed that uncoated superalloy suffered intense spalling and the weight change was massive during each cycle on studies of hot corrosion 900°C. The 100 per cent NiCr and 10 per cent (Cr₃C₂) – 90 per cent (NiCr) coatings provided better protection to T22 steel against the hot corrosion because of the formation of Ni and Cr₃C₂ layers.

In this research a variety of coatings have been used. This research work has been aimed to investigate the hot corrosion behavior of Boiler Steel b with different Cr₃C₂–NiCr coatings, under molten salt environment in Silicon tube furnace at 900°C, under cyclic conditions.

The purpose of this paper is to develop the high pressure high-velocity oxy-liquid fuel sprayed WC-10Co-4Cr coatings on geothermal turbine 9Cr-1Mo steel for protection against wear and corrosion.

The microstructural characterization of as-deposited and corroded coating was done and presented using X-ray diffraction and scanning electron microscope/energy dispersive spectroscopy analysis.

The developed coating offered 50 per cent enhanced microhardness (1,200 HV) and 100 per cent enhanced wear resistance, in comparison to bare geothermal turbine steel, respectively. The coating has shown enhanced life in the simulated working conditions (fog test and dip test). This may be because of the high microhardness of the developed coating as per the proven tribological theories.

Coating offered excellent corrosion resistance in the harsher simulated environments to geothermal turbines.

The purpose of this study is to investigate the effect of laser scanning speed (LSS) on the corrosive-tribological performance of Ni-60%WC coating in Wusu mine water, which was beneficial to improve the friction–wear performance of cylinder liner on water injection pump.

Ni-60%WC coatings were fabricated on 45 steel by laser cladding, and the microstructure and tribological performance was analyzed using a super depth of field microscope and ball-on-plate friction tester, and the wear mechanism was also discussed.

At room temperature (RT, 25 ± 2 °C), the average coefficients of friction of substrate and Ni-60%WC coatings fabricated at the LSS of 6, 10, 12 and 14 mm/s are 0.48 ± 0.08, 0.23 ± 0.01, 0.21 ± 0.05, 0.22 ± 0.02 and 0.25 ± 0.04, respectively, and the corresponding wear rates are 8.755 × 10⁴, 4.525 × 10³, 1.539 × 10³, 1.957 × 10³ and 2.743 × 10³ µm³·s^–1·N^–1, respectively, showing that the coating fabricated at the LSS of 10 mm/s has best friction reduction and wear resistance. The wear mechanism of Ni-60%WC coating is abrasive wear, fatigue wear and oxidative wear, which is resulted from the WC particles with the high-hardness.

Ni-60%WC coatings were first applied for cylinder liner, and the effect of laser scanning speed on its tribological performance was investigated.