The role of deposition temperature and scanning speed in the functional performance of laser assisted cold sprayed (LACS) coatings

Abstract: The functional performance of laser assisted cold sprayed (LACS) commercially pure ( CP) grade 1 titanium coatings was elucidated in terms of its mechanism of densification, microstructural evolution and corrosion resistance as the deposition temperature and scanning speed were altered by employing optical microscopy (OM) and potentio-dynamic polarization technique. The outcome of this study indicates that the densification mechanism of the coating was mainly influenced by the ratio of the processing temperature (T) and the scanning speed (SS) which is designated as . The attainment of the optimised functional properties of the coatings could be attributed to the thermal shear in the titanium film as well as its solid state inter-particulate consolidation resulting from localised thermal gradient which was induced between the ductile titanium particles and the brittle oxide film covering it at the optimum laser-gas-material interaction obtained at 600oC/10mm/s coupled with the adiabatic shearing of the particles upon impact at the deposition site. It was also established that microstructural porosity and cracks resulted from the increased lifetime of the liquid phase under suboptimal processing conditions which allowed more time for the propellant gas to initiate bubble formation within the coating’s microstructure. In addition, non-optimal parameters failed to attain the most desirable microstructural properties and corrosion resistance for the coatings. Finally, key factors in optimising LACS process parameters in order to achieve fully dense coatings are outlined

Investigation the effect of porosity on corrosion resistance and hardness of wc-co coatings on metal substrates

Abstract: Porosity is an important coating feature which strongly influences coating properties. Porosity creates poor coating cohesion and allows for higher corrosion rate and wear, and is generally associated with a higher number of unmelted or solidified particle that become trapped in the coating [1]. This investigation was conducted to investigate the effect of porosity on the hardness and corrosion resistance of WC-17Co coating on metal substrates. Coating of about 200μm were successful deposited by HVOF techniques unto four metal substrates, namely brass, 304L stainless steel, super-invar and aluminium. The corrosion behaviour was examined in chloride medium using direct current (DC) polarization test. The Vickers hardness was undertaken at loads of 5 kg for 10 s. The microstructures of the coatings were studied before and after the corrosion tests by scanning electron microscopy with EDX. The results indicated a strong correlation between porosity and corrosion rate, as well as hardness of the WC-17Co coatings

Effect of coating thickness on wear performance of Inconel 625 coating

Abstract: INCONEL® nickel-chromium alloy 625 is widely used for its high strength, excellent corrosion resistance and creep resistance on prolonged exposure to aggressive environment. However, despite its properties and industrial application, its wear resistance is not entirely satisfactory. The article investigates and presents the tribological performance of Inconel 625 coating using reciprocating scratch test. High velocity oxyfuel (HVOF) method was used to deposit Inconel 625 film onto 304 stainless steel surfaces. The frictional behavior and wear data were studied in order to observe the effect of coating thickness on wear failure. The results revealed that coatings of higher thickness showed lower coefficient of friction, better adhesion and good wear resistance in comparison to the low coating thickness

Atomic force microscopy analysis of surface topography of pure thin aluminium films

Abstract: Pure aluminium thin films were deposited on stainless and mild steel substrates through rf magnetron sputtering at rf powers of 150 and 200 W. Surface analysis of the films was undertaken using atomic force microscopy. The surface structure evolution, roughness and distribution were examined and discussed. Power spectral density, skewness and Kurtosis parameters were used to explain the nature and distribution of the surface structures on the thin aluminium films as reported from the line profile analyses. The result shows that the morphologies of the surface structures of Al films vary with power and substrate type. The coatings exhibit the higher roughness at 200 W. There is strong links that exist between AFM observations and SEM. This implies that AFM can be considerably used to study the microstructural evolution of Al thin films during magnetron sputtering

Effect of [Tris(trimethylsiloxy)silyethyl]dimethylchlorosilane on the corrosion protection enhancement of hydrophobic film coated on AISI 304

Abstract: The effects of Organofunctional moieties and the adhesion properties of hydrophobic [Tris(trimethylsiloxy)silyethyl]dimethylchlorosilane (Alkyl)] coated on AISI 304 to determine the corrosion resistance were investigated and presented. Two different types of adhesion, namely: silicon oxide and plasma silicon oxide films were grown on AISI 304 with the aid of an atomic‐layer deposition technique. The effects of the surface preparations on the functionality and the properties of the hydrophobic silane coating were characterized, using the scanning electron microscope (SEM) and the atomic force microscope (AFM) for morphology and topography. X‐ray diffraction (XRD) and attenuated Fourier‐transform infrared (FTIR‐ATR) were used for the chemical composition and the bonding structure, the water contact angle were measured and processed, as well as the determination of electrochemistry of the coated and uncoated surfaces. The results showed that the silicon oxide treated surface improved the durability of the silane film in the corrosive medium; and that has more chemical stability with the coating, when compared with the plasma silicon oxide and base material, which was distinctly discussed

Influence of surface treatment on dry sliding wear behavior of hydrophobic silane coating on AISI 304

Abstract: Henicosyl-1,1,2,2-tetrahydrododecyltricholrosilane is a hydrophobic silane compound coated on AISI 304 substrate. The surface of the substrate was treated in two ways (silicon oxide and plasma oxide) for adhesion and interface between the inorganic substrate and organic coating. The wear performance of the coating as a comparison to the AISI 304 was investigated using vacuum tribometer and characterized by scanning electron microscope and atomic force microscope. The result showed that the silane compound did improve the wear property of the AISI 304 stainless steel. It also proved that silane can be used as wear resistance agent

Experimental study of ZrB2-Si3N4on the microstructure, mechanicaland electrical properties of high grade AA8011 metal matrixcomposites

The present study evaluates the hybrid effect of ZrB2-Si3N4on the properties of AA8011 metal matrixcomposites (AMMCs) developed by two steps stir casting process. The percentage of reinforcement variesfrom 0% to 20% weight. The microstructure, hardness, ultimate tensile strength, yield strength, electricalresistivity, and conductivity were examined. From the results, it was revealed that the mechanicalproperties of the reinforced alloy are well improved compared to the unreinforced alloy. The opticalmicrograph and the scanning electron micrograph images with energy dispersive spectroscopy show theuniform distribution of the hybrid particulates of ZrB2-Si3N4with no visible porosity. The electrical re-sistivity of the developed AA8011 composites was also improved with the increase in weight percent ofthe ceramic particulates, but the electrical conductivity was drastically reduce

Experimental study of ZrB2-Si3N4 on the microstructure, mechanical and electrical properties of high grade AA8011 metal matrix composites

The present study evaluates the hybrid effect of ZrB2-Si3N4 on the properties of AA8011 metal matrix composites (AMMCs) developed by two steps stir casting process. The percentage of reinforcement varies from 0% to 20% weight. The microstructure, hardness, ultimate tensile strength, yield strength, electrical resistivity, and conductivity were examined. From the results, it was revealed that the mechanical properties of the reinforced alloy are well improved compared to the unreinforced alloy. The optical micrograph and the scanning electron micrograph images with energy dispersive spectroscopy show the uniform distribution of the hybrid particulates of ZrB2-Si3N4 with no visible porosity. The electrical resistivity of the developed AA8011 composites was also improved with the increase in weight percent of the ceramic particulates, but the electrical conductivity was drastically reduced