Abstract:Cobalt-phosphorus (Co-P) alloy is a promising material for the replacement of traditional hard chromium alloy of high hardness. In this paper, the cobalt-phosphorus alloy layer with high phosphorus content was formed by electrodeposition in a cobalt sulfate solution system under direct current (DC), single pulse (SP) current and double pulse (DP) current, separately. Surface morphology, structure and properties of the deposited layer were characterized by scanning electron microscopy (SEM), transmission electr… Show more
“…This indicates two structural transitions occur at these two temperature points. According to previous literature, the former peak primarily indicates the crystallization of the deposit, while the latter corresponds to the formation of Co–P compounds [1]. Figure 1 DSC curve recorded on Co–P–TiO 2 .…”
Section: Resultsmentioning
confidence: 71%
“…Despite its outstanding mechanical performance, electrodeposited hard chromium (EHC) is now facing the growing environmental and health concerns. To develop a replacement material for the widely applied EHC coating, the existing study is focusing on some promising candidate materials including Ni-P, Ni-Co and Co-P [1]. Among these, Co-P coating material is gaining increasing research attention due to its advantages in hardness, thermal stability, wear resistance and corrosion resistance [2][3][4].…”
The effects of heat treatment on the properties of electrodeposited Co-P-TiO 2 nanocomposite coatings were systematically investigated. The TiO 2 nanoparticles-reinforced Co-P-TiO 2 nanocomposites were heat-treated at different temperatures. Thermal analysis was conducted to characterize the structural transitions. The phase constituents and surface morphology of nanocomposites were identified. The mechanical properties including microhardness and wear tests were examined, and the electrochemical behaviour of Co-P-TiO 2 was determined. At the increasing heating temperature, the structure of Co-P-TiO 2 was gradually changed from amorphous into crystalline, with its surface morphology being smoother. Proper heat treatment can significantly improve the mechanical properties and corrosion resistance of coatings. When Co-P-TiO 2 coating was heat-treated at 350°C, a smooth and flat surface morphology was obtained and optimal physicochemical performance among the examined coatings was achieved.
“…This indicates two structural transitions occur at these two temperature points. According to previous literature, the former peak primarily indicates the crystallization of the deposit, while the latter corresponds to the formation of Co–P compounds [1]. Figure 1 DSC curve recorded on Co–P–TiO 2 .…”
Section: Resultsmentioning
confidence: 71%
“…Despite its outstanding mechanical performance, electrodeposited hard chromium (EHC) is now facing the growing environmental and health concerns. To develop a replacement material for the widely applied EHC coating, the existing study is focusing on some promising candidate materials including Ni-P, Ni-Co and Co-P [1]. Among these, Co-P coating material is gaining increasing research attention due to its advantages in hardness, thermal stability, wear resistance and corrosion resistance [2][3][4].…”
The effects of heat treatment on the properties of electrodeposited Co-P-TiO 2 nanocomposite coatings were systematically investigated. The TiO 2 nanoparticles-reinforced Co-P-TiO 2 nanocomposites were heat-treated at different temperatures. Thermal analysis was conducted to characterize the structural transitions. The phase constituents and surface morphology of nanocomposites were identified. The mechanical properties including microhardness and wear tests were examined, and the electrochemical behaviour of Co-P-TiO 2 was determined. At the increasing heating temperature, the structure of Co-P-TiO 2 was gradually changed from amorphous into crystalline, with its surface morphology being smoother. Proper heat treatment can significantly improve the mechanical properties and corrosion resistance of coatings. When Co-P-TiO 2 coating was heat-treated at 350°C, a smooth and flat surface morphology was obtained and optimal physicochemical performance among the examined coatings was achieved.
During recent decades, CoP alloy deposits have gained enormous attention primarily owing to their favorable tribomechanical properties; therefore, they are regarded as a potential alternative to hard chromium coatings. The previous works on these systems usually addressed the approaches to improve their tribomechanical characteristics. However, to increase the industrial applications, especially in marine environments, enhancement of corrosion performance should also be considered. The focus of this investigation is improving the corrosion properties of CoP deposits through the incorporation of hybrid nanoparticles, i.e., MoS 2 and Y 2 O 3 , as well as controlling the applied current density. Microstructural and morphological aspects of the coatings were characterized by XRD, EDS, FE-SEM, and AFM. While the surface morphology of the CoP alloy deposit contains several surface defects, MoS 2 + Y 2 O 3 reinforced ones are compact and composed of nodular grains. Although there is no change in morphology of the nodular grains with current density variation, the surface roughness increases by increasing the current density from 15 to 25 A dm À2. Influences of both nanoparticle loadings in the electrolyte and the applied current density on the corrosion performance of the deposits are addressed in detail. Overall, the results confirmed that the CoP -4 g/L MoS 2 + Y 2 O 3 nanocomposite coating electrodeposited at 25 A dm À2 has the highest corrosion resistance against 3.5 pct NaCl solution, % 10 times higher than that of CoP .
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