Abstract
To enhance the erosion-corrosion resistance of titanium alloys, two Ta(Si1−xAlx)2 coatings with different Al content were deposited on Ti−6Al−4V alloy by double cathode glow discharge method. The coatings consist of single hexagonal C40 structured TaSi2 phase, which forms an equiaxed grain structure with an average diameter of ∼5 nm. Al addition was found to enhance the values of H/E and adhesive strength between the substrate and coating. The erosion–corrosion behavior of the coatings was studied in a liquid–solid acid slurry flow (specifically a medium of 5 wt% HCl solution that contained a 10 wt% concentration of silica-based sand) using electrochemical measurements, weight loss tests and SEM observation. The results indicated that the ternary Ta(Si0.875Al0.125)2 coating provided better protection, compared to the binary TaSi2 coating, against the combined attack of mechanical erosion and electrochemical corrosion in a liquid–solid acid slurry flow. This is attributable to high self-healing ability of the surface passive film and a higher H/E ratio.
Highlights
As one of the most frequent material deterioration phenomena, erosion-corrosion damage is often found in many industrial operations involved in fluid handling, such pipelines, power plants, hydraulic turbines, marine and off-shore equipment etc [1, 2]
The results indicated that the ternary Ta(Si0.875Al0.125)2 coating provided better protection, compared to the binary TaSi2 coating, against the combined attack of mechanical erosion and electrochemical corrosion in a liquid–solid acid slurry flow
Phase composition and microstructure of Ta(Si1−xAlx)2 coatings Figure 2 shows typical x-ray diffraction (XRD) patterns obtained from both binary TaSi2 and ternary Al containing TaSi2 coatings, along with the powder diffraction file data (JCPDS Card No 38–0483) of hexagonal C40 structured TaSi2. It can be seen from figure 2 that the two as-received Ta(Si1−xAlx)2 coatings have similar patterns where all characteristic diffraction peaks are well matched with that of hexagonal C40 structured TaSi2
Summary
As one of the most frequent material deterioration phenomena, erosion-corrosion damage is often found in many industrial operations involved in fluid handling, such pipelines, power plants, hydraulic turbines, marine and off-shore equipment etc [1, 2]. Under these conditions, industrial components often suffer from the joint action of mechanical erosion and electrochemical corrosion processes, through the action of solid erodent particles entrained in a corrosive fluid [3]. It is essential to consider all these relevant factors in the design of high performance erosion-corrosion resistant material suitable for harsh environment
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