TRIBO-MECHANICAL CHARACTERIZATION OF ENB ALLOY COATINGS: EFFECT OF HEAT-TREATMENT TEMPERATURE AND SODIUM BOROHYDRIDE CONCENTRATION

Previously electroless Ni-B (ENB) coatings were analyzed and optimized based on various coating parameters. However, variation of nano-indentation behaviour like nano-hardness, elastic modulus and scratch hardness variation with bath composition and heat treatment temperature has not been reported earlier. An attempt has been made to explore the same in the present study. ENB coating layers are deposited on AISI 1040 steel specimen with varying concentration of  sodium borohydride (NaBH4) and heat-treated at 350°C, 450°C and 550°C to investigate the related effects. Nano-hardness and elastic modulus of as-coated specimens are found to improve with NaBH4 concentration due to increased boron content and nodule size. Both nano-hardness and elastic modulus are observed to improve further upon heat treatment because of incorporation of various boride phases leading to compact morphology and increased size of the nodules. Scratch hardness value also increases with NaBH4 concentration and it improves further upon heat treatment and reaches to its maximum at 450°C due to presence of compact and hard Ni2B phase. Compact homogeneous surface morphology enhances the friction and wear behaviour of the heat-treated coatings even though surface roughness deteriorates after heat treatment.

Friction Properties of the Heat-Treated Electroless Ni Coatings Embedded with c-BN Nanoparticles

The nickel (Ni) coatings without and with embedded (5-7 vol. %) cubic boron nitride (c-BN) nanoparticles (10 nm in diameter) were deposited on carbon steel substrate by an electroless plating process. Coatings were tested in as-deposited and heat-treated (heating at 300 degrees C for 6 h) conditions. Coating structure characterisation was performed, as well as hardness and roughness measurements. Friction properties were tested in dry and in water (seawater) lubricated contact conditions, with bronze as a counter-body material. Both static and kinetic coefficients of friction were measured for two different surface texture preparations (initial and working). The first surface texture simulated the running-in condition, and the second surface texture represented the steady-state conditions. The enhancement of the abrasive and erosive wear resistance of heat-treated electroless Ni coatings with embedded c-BN nanoparticles was already proved in our previous studies. This study aims to investigate those influences on friction properties of electroless Ni coatings in different sliding conditions. The results show that the coefficients of friction did not differ too much between the coatings and that the surface roughness and presence of seawater had a much stronger influence

Wear behaviour of electroless heat treated Ni-P coatings as alternative to electroplated hard chromium deposits

In this present study was evaluated the influence of heat treatment on the wear resistance of electroless high phosphorus nickel coating (9-10% P wt.). In addition, both untreated and treated Ni-P deposits were then compared to electroplated hard chromium coatings in terms of wear behaviour. Three different heat treatment conditions were performed at temperatures of 320ºC, 400ºC and 500ºC under different holding times. The selection of the heat treatment conditions was chosen considering the results obtained by a differential scanning calorimetry (DSC) analysis. The wear behaviour of the Ni-P samples was investigated through a non-lubricated “ball on plate” test carried out against an Al2O3 counter-face. After an analysis of the friction coefficient, microstructure of the worn surface, width and chemical composition of the wear track, was possible to conclude that the heat treatment affect positively the wear resistance of Ni-P coatings. Treatment conditions of 320ºC with 9 hours holding time and 400ºC with 1 hour holding time showed the best results due to a structural change from amorphous supersatured solid solution of phosphorus in nickel to a crystalline structure of nickel crystallites and nickel phosphides (Ni3P) occurred between 320ºC and 360ºC that was verified after x-ray diffraction analysis. Moreover, Ni-P heat treated coatings showed better results when compared to electroplated hard chromium deposits, hence acting as a natural alternative for chromed coatings

Abrasive Resistant Coatings—A Review

Abrasive resistant coatings have been widely used to reduce or eliminate wear, extending the lifetime of products. Abrasive resistant coatings can also be used in certain environments unsuitable for lubrications. Moreover, abrasive resistant coatings have been employed to strengthen mechanical properties, such as hardness and toughness. Given recently rapid development in abrasive resistant coatings, this paper provides a review of major types of abrasive coatings, their wearing mechanisms, preparation methods, and properties

Effect of heat treatment on the tribological properties of Nickel-Boron electroless coating

Nickel-Boron autocatalytic coatings are widely used in several industries to improve mechanical properties of materials such as hardness and wear resistance. Tribological properties were evaluated in Ni-B autocatalytic coatings deposited on AISI/SAE 1018 carbon steel before and after a heat treatment at 450 °C for one hour. Tribological tests were carried out by dry sliding, using a load of 5 N and a sliding speed of 0.012 m/s, in a homemade ball-on-disk tribometer, which followed ASTM G99 standard. According to the tribological evaluation, the heat treatments applied to Ni-B coatings improved their tribological performance. This research corroborates that by applying an adequate heat treatment, hardness and wear resistance of Ni-B coatings can be improved significantly

Electroless Plating of Ni-B Composite Coating on AZ31 Mg alloy

A Ni–B coating was electroless-deposited directly on H3PO4/HF pickled AZ31. The thickness of the plating layer was estimated through weight gain measurements and was affected by temperature, time and bath composition. The highest thickness was obtained at 6 g/L of NaHB4 at 85oC.  An adherent compact layer of Ni-B was obtained. Electrochemical impedance spectroscopy measurements in 3.5 wt.% sodium chloride aqueous solution suggest that the plating can protect the magnesium alloy substrate from corrosion attack

Tribological Comparison of Traditional and Advanced Firearm Coatings

The objective of this project is to find which type of coating has the best performance characteristics for finishing firearms. This is accomplished by measuring and comparing several performance characteristics, such as: adhesion, hardness, wear resistance, friction control, and corrosion resistance. Appearance is not a factor since any exterior coating that is flashy can be subdued or camouflaged with special purpose paints, which have proven durable enough for such purposes. Cost will not be a limiting factor for this experiment, but will be discussed in the conclusion as a secondary concern. This data will be used to identify the best coating for steel and aluminum firearm parts. The goal is to lengthen a firearm’s life cycle while increasing performance and reliability by applying the best coating

Efeito do tratamento térmico sobre as propriedades tribológicas do recobrimento autocatalítico níquel-boro

1 recurso en línea (páginas 101-110).Os recobrimentos autocatalíticos de níquel-boro são utilizados em diferentes indústrias para melhorar as propriedades mecânicas de materiais, como a dureza e a resistência ao desgaste. Nesta pesquisa avaliaram-se as propriedades tribológicas de recobrimentos autocatalíticos Ni-B depositados sobre aço ao carbono AISI/SAE 1018 antes e depois de aplicar um tratamento térmico a 450 °C durante 1 hora. Adicionalmente, realizaram-se ensaios tribológicos por deslizamento em seco, utilizando uma carga de 5 N e uma velocidade de deslizamento de 0.012 m/s, em um tribômetro ball-on-disk fabricado pelo CIDEMAT de acordo com a norma ASTM G99. De acordo com a avaliação tribológica, estabeleceu-se que o tratamento térmico aplicado melhora significativamenteo rendimento tribológico dos recobrimentos autocatalíticos Ni-B.Los recubrimientos autocatalíticos de níquel-boro son utilizados en diferentes industrias para mejorar las propiedades mecánicas de materiales, como la dureza y la resistencia al desgaste. En esta investigación se evaluaron las propiedades tribológicas de recubrimientos autocatalíticos Ni-B depositados sobre acero al carbono AISI/SAE 1018 antes y después de aplicar un tratamiento térmico a 450 °C durante 1 hora. Adicionalmente, se realizaron ensayos tribológicos por deslizamiento en seco, utilizando una carga de 5 N y una velocidad de deslizamiento de 0.012 m/s, en un tribómetro ball-on-disk fabricado por el CIDEMAT de acuerdo con la norma ASTM G99. De acuerdo con la evaluación tribológica, se estableció que el tratamiento térmico aplicado mejora significativamente el rendimiento tribológico de los recubrimientos autocatalíticos Ni-B.Nickel-Boron autocatalytic coatings are widely used in several industries to improve mechanical properties of materials such as hardness and wear resistance. Tribological properties were evaluated in Ni-B autocatalytic coatings deposited on AISI/SAE 1018 carbon steel before and after a heat treatment at 450 °C for one hour. Tribological tests were carried out by dry sliding, using a load of 5 N and a sliding speed of 0.012 m/s, in a homemade ball-on-disk tribometer, which followed ASTM G99 standard. According to the tribological evaluation, the heat treatments applied to Ni-B coatings improved their tribological performance. This research corroborates that by applying an adequate heat treatment, hardness and wear resistance of Ni-B coatings can be improved significantly.Bibliografía: página 110