1,721,111 research outputs found
Solid particle erosion–corrosion behaviour of a novel HVOF nickel aluminium bronze coating for marine applications—correlation between mass loss and electrochemical measurements
No full textThis paper investigates the solid particle erosion–corrosion performance of an experimental high velocity oxy-fuel (HVOF) sprayed nickel–aluminium bronze (NAB) coating using conventional gravimetric techniques as well as in situ electrochemical analysis. The coating consists of HVOF powders from three alloys: stainless steel alloy, nickel-based alloy and aluminium bronze alloy. It is a candidate coating for marine applications as a cost effective replacement of existing castings and to improve component life. The coating was subjected to pure erosion, flow corrosion and erosion–corrosion tests. A jet impingement slurry erosion rig was used to carry out the experiments; the effects of jet velocity were investigated. By gravimetric analysis the degree of synergy was evaluated and a constant was revealed which described to what extent the presence of corrosion products/films reduces the erosivity and promotes negative synergy. Likewise, standard deviations of electrochemical current measurements are shown to reveal the presence of protective film formation under flow corrosion and film breakdown under erosion–corrosion conditions. Separation of the erosion-enhanced corrosion component revealed that at high erodent kinetic energies, erosion-enhanced corrosion dominates and generates a positive synergy. At lower energies, this coating system forms a protective film which reduces the contact conditions on impingement and a negative synergy results. Overall, correlations between the mass loss and electrochemical measurements have been established and were used to identify and quantify synergy
The slurry erosion behaviour of high velocity oxy-fuel (HVOF) sprayed aluminium bronze coatings
No full textThis paper investigates the erosion aspects of a novel high velocity oxy-fuel (HVOF) sprayed aluminium bronze coating under sand particle impingement conditions, using a free-jet impingement erosion rig. Erodents at various kinetic energies (0.1–0.8 ?J) and impingement angles (30, 60 and 90°) were used to simulate actual service conditions. Gravimetric measurements, surface profilometry and microscopy techniques were utilised to determine both the erosion rate and the mechanisms of coating failure. The erosion rate of the coating was found to be comparable to bulk 90/10 cupro-nickel (C70600) and about twice that of Marinel and AISI 316L stainless steel. These results suggest that HVOF aluminium bronze coatings are suitable candidates for marine applications. Analysis of the erosion scars suggest that coating erosion occurred by a combination of cutting wear, plastic deformation, and crack propagation at splat boundaries (brittle oxides) leading to the detachment of coating splats, cutting wear was found to be the most dominant. The cutting process was dominated by smaller particle impacts. The number of these particles which cause damage appears to be a function of kinetic energy
Electrochemical investigation of high velocity oxy-fuel (HVOF) aluminum bronze coatings under slurry erosion in saline environments
No full textErosion and erosion-corrosion performance of cast and thermally sprayed nickel-aluminium bronze
No full textNickel-Aluminum Bronze (NAB) is widely used for propulsion and seawater handling systems in naval platforms. It is selected because of its attractive combination of toughness and shock resistance but it has inherent susceptibility to selective phase corrosion and erosion-corrosion. In order to extend the life of NAB components, modern coating techniques are being considered in order to confer improved wear and corrosion resistance, as well as a method of providing cost effective refurbishment. This paper presents research into erosion and erosion-corrosion of both "as cast" and thermally sprayed NAB. The synergistic effects based on mass loss measurements obtained from pure erosion (E), flow corrosion (C) and erosion-corrosion (T) experiments are presented under a range of energies that relate to maritime operation conditions. The influence of synergy was found to be dependent on flow energy and could be either beneficial or detrimental. The results of this work assist with material selection for controlled or reduced material loss in marine vessels
Erosion and erosion–corrosion performance of cast and thermally sprayed nickel–aluminium bronze
No full textNickel–aluminium bronze (NAB) is widely used for propulsion and seawater handling systems in naval platforms. It is selected because of its attractive combination of toughness and shock resistance but it has inherent susceptibility to selective phase corrosion (SPC) and erosion–corrosion. In order to extend the life of NAB components, modern coating techniques are being considered in order to confer improved wear and corrosion resistance, as well as a method of providing cost effective refurbishment. This paper presents research into erosion and erosion–corrosion of both “as-cast” and thermally sprayed NAB. The synergistic effects based on mass loss measurements and electrochemical techniques obtained from pure erosion (E), flow corrosion (C) and erosion–corrosion (T) experiments are presented under a range of energies that relate to maritime operating conditions. The influence of synergy was found to be dependent on flow energy and could be either beneficial or detrimental. Comparison of the erosion performance with that of the erosion–corrosion performance both coating and cast surfaces demonstrate a propensity for negative synergy. However, vulnerability at high energies to positive synergy was seen for the coating. The results of this work assist with material selection for controlled or reduced material loss in marine vessels
Investigation of erosion-corrosion processes using electrochemical noise measurements
No full textThis paper presents an example-based discussion of erosion–corrosion and flow corrosion processes that have been identified using electrochemical noise measurements. Various single and dual phase corrosion and erosion–corrosion experiments on austenitic stainless steels and various thermally sprayed coatings using jet impingement and pipe flow rigs are discussed. Localised corrosion events, metastable and propagating pitting, passive and general corrosion processes have been identified under various flow conditions of NaCl solutions. Oscillations in the electrochemical potential noise signals have been related to an erosion-enhanced corrosion synergistic effect. Electrochemical noise measurements show responses to electrolyte permeation of the coating, coating erosion penetration and substrate activity under erosion–corrosion conditions
Electrochemical investigation of high velocity oxy-fuel (HVOF) aluminium bronze coatings under slurry erosion in saline environments
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