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This paper aims to compare the wear behavior, surface roughness, friction coefficient and volume loss of high-velocity oxy-fuel (HVOF) sprayed WC–Co and WC–Cr₃C₂–Ni coatings on AISI 1095 steel with spraying times of 10 and 15 s.

In this study, the pin-on-disc testing technique was used to evaluate the wear characteristics at a speed of 0.24 m/s, load of 40 N and test time of 60 min under dry conditions at room temperature. The wear characteristics were examined and analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The surface roughness of a coated surface was measured, and microhardness measurements were performed on the cross-sectioned and polished surfaces of the coating.

Spraying time and powder material affected the hardness of HVOF coatings due to differences in the porosity of the coated layers. The average hardness of the WC–Cr₃C₂–Ni coating with a spaying time of 15 s was approximately 14% higher than that of the WC–Cr₃C₂–Ni coating with a spraying time of 10 s. Under an applied load of 40 N, the WC–Co coating with a spraying time of 15 s had the lowest variation in the friction coefficient compared with the other coatings. The WC–Co coating with a spraying time of 10 s had the lowest average and variation in volume loss compared to the other coatings. The WC–Cr₃C₂–Ni coating with a spraying time of 10 s exhibited the highest average volume loss. The wear features changed slightly with the spraying time owing to variations in the hardness and friction coefficient.

This study investigated tribological performance of WC–Co; WC-Cr₃C₂-Ni coatings with spraying times of 10 and 15 s using pin-on-disc tribometer by rotating the relatively soft pin (C45 steel) against hard coated substrate (disc).

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.

The purpose of this paper is to investigate the combined erosion and corrosion behavior of WC-Ni vacuum brazed coating.

Al₂O₃ particles and 10 wt% NaCl solution are used to evaluate erosion and corrosion resistance of WC-Ni vacuum brazed coating. Combined test of erosion and corrosion is also conducted. The microstructure of each specimen is characterized by the scanning electron microscopy. The chemical composition was determined by energy-dispersive X-ray spectroscopy.

WC-Ni vacuum brazed coating layer is effective protective coating under combined erosion and corrosion environment. The weight loss of coating layer is more reduced as the cumulative test time.

WC-Ni vacuum brazed coatings are investigated to check characteristic of the combined erosion and corrosion environment. WC-Ni vacuum brazed coatings are kind of diffusion coating that attract attention because of the resistance of superb impact and corrosion in comparison with other coatings. Some previous researches reported the properties of vacuum brazed WC material. Erosion and corrosion behaviors of WC-Ni vacuum brazed coatings were studied in our previous research, respectively. Hence, in this research, the principal objective is to examine the combined erosion and corrosion behavior of WC-Ni vacuum brazed coating.

The purpose of this paper is to investigate the tribological properties of the WC/TiC-Co substrate under different loading conditions under three impact abrasive wear conditions.

The three body collisional wear behavior of Co alloy with WC and TiC at three impact energy was studied from 1 to 3 J. Meanwhile, the microstructure, hardness, phase transformation and wear behavior of these specimens were investigated by scanning electron microscopy, Rockwell hardness (HRV), EDS and impact wear tester. The resulting wear rate was quantified by electronic balance measurements under different pressures.

The specific wear rate increases with the increase of the nonlinearity of the impact energy and the increase in the content of WC or TiC. The effect of TiC on wear rate is greater than that of WC, but the hardness is smaller. The wear characteristics of the samples are mainly characterized by three kinds of behavior, such as cutting wear, abrasive wear and strain fatigue wear. The WC-Co with fewer TiC samples suffered heavier abrasive wear than the more TiC samples under both low and high impact energy and underwent fewer strain fatigue wears under high impact energy.

The experimental results show that the wear resistance of the Co alloy is improved effectively and the excellent impact wear performance is achieved. The results can be used in cutting tools such as coal mine cutting machines or other fields.

In this study, electrochemical deposition method which have cheaper equipment than thermal spraying methods and is available for the production of composite coatings were used.

Composite coatings were electrodeposited from a Watts's bath solution in which the suspended Cr₃C₂-NiCr particles were dispersed in the bath solution during deposition. Potentiodynamic polarization and electrochemical impedance spectroscopy techniques have been used to evaluate the corrosion resistance of the composite coating in the 3.5 Wt.% NaCl solution.

It was found that the submicron Cr₃C₂-NiCr particles distributed uniformly in the coating and depend on the current density of deposition, different amount of particles can be incorporated in the coating. The results showed that the corrosion resistance of the Ni/ Cr₃C₂-NiCr composite coatings is more comparable to the pure nickel coating.

Production of Ni-base composite coating from an electrolytic bath containing Cr₃C₂-NiCr particles is possible via electrodeposition.

The reduction of wear by the use of sprayed surface coatings holds considerable potential at a time when Industry is becoming more conscious of the need to reduce its operating costs. Control of wear is unlikely to become a true science due to the arbitrary nature of the conditions that produce the effect and although no truly economic solution exists for completely preventing surface degradation, it can be minimized to acceptable limits. It is the purpose of this article to present an approach to the use of sprayed surface coatings in tribological situations. Common wear types are briefly described and the philosophy behind the protective surface layer in relation to surface geometry is outlined. The performance of sprayed coatings in adhesive and abrasive wear situations is evaluated and discussed. In addition, the use of sprayed deposits for lubricated bearing surfaces is considered as well as the application of low friction coatings by the spray method.

This paper aims to use the high-velocity oxy fuel (HVOF) spraying process for depositing 93(WC–Cr₃C₂)–7Ni, 75Cr₃C₂–25NiCr, 83WC–17C_O and 86WC–10C_O–4Cr coatings on ASME SA213 T91 to study the corrosion resistance of these coatings in an actual boiler environment.

The HVOF spraying process was used for depositing 93(WC–Cr₃C₂)–7Ni, 75Cr₃C₂–25NiCr, 83WC–17C_O and 86WC–10C_O–4Cr coatings on ASME SA213 T91. All the coatings obtained are found to be uniform, dense and having thickness between 200 and 250 μm. All the coatings were exposed in an actual boiler environment at 900°C temperature for 10 cycles. Each cycle consisted of 100 h heating followed by 1 h cooling at ambient conditions. X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy techniques were used to analyse corrosion products.

All the coated samples were found to be having higher corrosion resistance than the uncoated samples. Among coated specimens, 93(WC–Cr₃C₂)–7Ni coating has shown maximum and 75Cr₃C₂–25NiCr coating has shown minimum resistance to corrosion.

This paper is original research.

The present work aims at developing the laser cladding technology by means of an active fiber laser source applicable for hardfacing of martensitic steel turbine blades. It also aims to investigate two process parameter conditions to reproduce two different heat inputs, in order to highlight the effect of the thermal input on the thermal alteration and dilution of the substrate material and clad layer.

The experimentation was performed initially at a sample level, reproducing the material and thickness of the blade leading edge, then on an industrial real component. Cladding process parameters were experimentally selected and two different process parameter conditions, at different specific energy, were determined. The microstructural and geometrical features of the clad samples were analyzed both by optical microscopy and scanning electron microscopy, in this latter case combining the information supplied by different probes, among which the EDX microanalysis to obtain chemical profiles. Hardness distribution was also evaluated by means of Vickers hardness tester.

All the two investigated conditions were suitable for laser cladding of the blade leading edge, since a crack and pore free clad layer with a strong metallurgical bond to the substrate was obtained. The experimented two different heat inputs affected the extension of the HAZ as well the chemical and geometrical dilution. The clad integrity was preserved in both cases. The condition at higher specific energy was chosen to clad the turbine blade. The high specific energy condition was preferred because the iron dilution in the clad layer was inferior.

Further research is needed to correlate the chemical dilution and the thermal alteration introduced by the laser cladding process on such a kind of substrate at different process parameter conditions to the wear and corrosion resistance of the turbine blade.

Laser cladding process with an innovative active fiber laser source of the leading edge of a steam turbine blade was developed. Progress achieved in laser cladding technology development is of practical value for manufacture of turbine blades, made of martensitic steels.

The paper investigates the effect of different energy input on the laser cladding of steam turbine blades, mainly used in coal, gas and nuclear plants to produce electricity by heating water to create steam. The laser cladding process is an effective technology to increase the steam blades toughness and resistance to creep, stress and corrosion. This increase in the turbine blade properties contributes to extend the life of such a critical components, decreasing cost and time of substitution and ensuring better service conditions.

The most original aspect of the paper is related to the focus on the difference between the chemical and the geometrical dilution, being the first one mainly related to the corrosion and wear resistance of the clad layer, while the later mainly regards the clad layer adhesion to the substrate. More in general the paper presents one of the first experiments accomplished while making use of the active fiber laser source.

This paper aims to perform the solid particle erosion studies in simulated coal-fired boiler conditions with a view to compare the erosion behavior of two different types of detonation gun (D-Gun) sprayed cermet coating powders, that is, WC-12%Co and Cr₃C₂-25%NiCr on ASTM A36 steel and bare (uncoated) ASTM A36 steel.

Erosion studies were performed using an air jet erosion test rig at impingement angles of 45°, 60° and 90°. During the erosion studies weight loss, erosion rates in terms of volume loss (mm³/g) and measurement of erosion profiles were determined using optical profilometer.

Both cermet coatings had successfully protected the ASTM A36 steel from erosion at impingement angles of 45°, 60° and 90°. In the case of bare ASTM A36 steel, the erosion rates were maximal at an impingement angle of 45° and minimal at an impingement angle of 90°, thus depicting the peculiar erosion behavior of ductile materials. WC-12%Co coated specimens exhibited erosion behavior that is closer to the behavior of ductile materials. Cr₃C₂-25%NiCr coated specimens exhibited the maximum erosion rate at an impingement angle of 90° and minimum at an impingement angle of 45°, hence depicting the typical behavior of brittle materials.

It is expected that these results will contribute to the improvement of erosion resistance of induced draft fans, by the application of D-Gun sprayed WC-12%Co and Cr₃C₂-25%NiCr cermet coatings.

This paper evaluates the solid particle erosion behavior of bare and cermet-coated ASTM A36 steel which will be helpful in choosing the suitable cermet coating for induced draft fan applications.

Discusses developments in coatings using high velocity oxyfuel (HVOF). Covers the basic process, comparisons with other thermal spraying processes and optimization of performance. Discusses industrial applications and new developments in the technology.