Effect of 200 days of cyclic weathering and salt spray on the performance of PU coating applied on a composite substrate

An appropriate clearance is required between mating gears for effective power transmission. In the present work, the effect of radial misalignment on mild wear of spur gear is modeled and simulated. The changes in the gear tooth contact geometry due to progressive wear have also been accounted in the model. The simulation results show that in the pinion dedendum region, pressure angle increases, while the contact pressure and wear depth decrease with increase in number of wear cycles. As far as the effect of radial misalignment is concerned, contact pressure decreases and wear depth increases with the increase in misalignment. In the pinion addendum region, pressure angle and wear depth increase with the increase in wear cycles, while the contact pressure and wear depth decrease with the increase in misalignment. The pressure angle and pitch point change from initial 20° (23rd pitch point) to 20.95° (26th pitch point) and 21.86° (28th pitch point) due to 0.5- and 1-mm radial misalignment, respectively. The wear depths after 50,000 wear cycles are − 1.32 × 10−2 μm, − 3.33 × 10−3 μm and − 4.39 × 10−4 μm at 23rd, 26th and 28th pitch points, respectively. The effect of radial misalignment on backlash, pressure angle, pitch point, contact ratio, double tooth contact region and speed ratio is also discussed.

ABSTRACT: In the process of exploration and development of extended-reach wells and ultra-deep wells, serious dogleg severity and high hardness formation, etc. will lead to casing exterior wear, thereby reducing the residual strength of the casing. However, the existing research on casing wear mainly studies the interior wear of casing caused by the rotation of drill pipe joints, and ignores the exterior wear caused by the contact between casing and well wall during casing running. As a consequence, the prediction model of casing exterior wear is established based on the wear efficiency model and the three-dimensional torque and drag model. Case study is conducted with this model and sensitivity analysis is also performed. The results show that the casing with the greatest exterior wear depth is located below the direction turning section. The wear depth decreases with the increase of the outer radius of the casing, and increases with the increase of the wellbore radius. In addition, with the increase of drilling fluid density, the wear depth of the upper casing increases, and the wear depth of the lower casing decreases. The casing collapse resistance after casing exterior wear is studied through numerical simulation. The results show that the collapse resistance of casing decreases with the increase of wear depth, and there is an approximate linear relationship between the two. The study provides a method to improve the prediction accuracy of casing wear, which is of great significance for the casing design and wellbore integrity. 1. INTRODUCTION With the development of drilling technology, horizontal well and extended reach technologies are widely used in the world. The wellbore conditions of extended-reach wells and horizontal wells with long horizontal sections are more complicated than conventional wells. Running casing is challenging due to the difficulty of hole cleaning, the high friction factor, the wellbore tortuosity, and the large lateral force acting on the wellbore by the casing, etc. Usually the casing needs to be picked-up and released many times, and the running time is long, so the outer wall of the casing is more likely to be worn, which reduces the residual strength of the casing.

Microstructure formation and corrosion behaviour in HVOF-sprayed Inconel 625 coatings

In the present study, a galvanized steel and a AA6082 aluminum alloy sheet of 2 mm thick were weld-brazed by applying laser and using 2-mm-diameter solid Al-12% Si filler wire at 2.5 m/min wire feed rate and 2 m/min laser scan speed at varying laser power (4.0, 3.5, 3.0 kW) in flange configuration. The microstructural investigation of the laser weld-brazed joints revealed the presence of two-layered intermetallic compound at steel/braze seam interface. The corresponding x-ray diffraction analysis of the steel/braze seam interface showed the presence of Al-Fe-Si-based ternary intermetallic phases. SEM and EDS analysis of the braze seam revealed the presence of α-Al grains surrounded by Mg2Si phase in the grain boundary region. Fine intermetallic layer was observed at lower heat-input condition. The corrosion performance of the brazed joints was studied with the help of immersion, salt spray, and electrochemical polarization tests in different electrolytes containing NaCl salt. Brazed joints experienced galvanic corrosion during immersed in corrosive media. From the salt spray test, it was revealed that galvanized steel was highly susceptible to corrosion compared to Al-rich phase. The polarization results showed a substantial change in corrosion resistance from steel interface to the brazed region due to the variation in microstructure. The samples brazed with low heat-input showed better corrosion resistance as compared to the joints made with high heat-input. Post-corrosion microstructure revealed intergranular corrosion at the brazed joint along with pit formation.

Corrosion resistance of the electro-galvanized steel treated in a titanium conversion solution

Traditional neutral salt spray tests fail to accurately simulate the accelerated corrosion that occurs under actual energized conditions. We have developed a salt spray test chamber capable of reducing the relative humidity (RH) in the testing environment to prevent short circuits, insulation failures, and other faults that lead to premature damage during testing. Initially, the effect of salt spray concentration on corrosion at 85 % RH was examined, and it was found that the corrosion rate does not increase when the concentration surpasses 50 mg/m3. The humidity-controllable salt spray test demonstrated a closer match to real environmental corrosion, judging by both the appearance of corrosion and the acceleration ratios across different metals, where the acceleration ratio difference between maximum and minimum values was reduced from 18.6 times to 1.4 times. The influence of RH on the corrosion rate was revealed, with the highest rate observed at 75 % RH. Lastly, we proposed optimal parameters for energized salt spray tests, evaluated the failure modes of several products under these tests, preliminarily confirmed the consistency and acceleration effects of this method for electrical products in real marine atmospheric conditions.

This study investigated the corrosion resistance of oil impregnated anodic aluminum oxide (AAO) surfaces of aluminum 7075 for subsea application. Although aluminum 7075 has high strength, it is scarcely used in the subsea industry because of its corrosion issue. Some treatment of aluminum 7075 is required for subsea application. In this study not only a plate shape but also a cylindrical shape were investigated because a cylindrical shape is frequently used in the subsea industry for electronic device housing. Contact angles of bare aluminum and oil impregnated AAO surfaces of aluminum 7075 were measured after a salt spray test and a pressure test. The results showed that the contact angle of bare aluminum was considerably decreased after the salt spray test, whereas the oil impregnated AAO surface presented a relatively high contact angle after the salt spray test and the pressure test. These results showed that the corrosion resistance of aluminum 7075 could be enhanced by oil impregnation on the AAO surface, and thus can be utilized in the subsea industry.

Nanoperiod multilayered films were deposited by controlling the time the substrate was positioned opposite each of the graphite and boron nitride semicircular targets. The wear depth of the 4-nm-period multilayered film is the lowest of all the sliding cycles; therefore, the wear resistance is clearly improved for a 4-nm-period layered film. To clarify the reason why the wear resistance of these multilayered films increases, the wear properties of the load conditions under which the wear increases atomically were evaluated by varying the number of sliding cycles. The wear depth increases with increasing the number of sliding cycles. The weardepth increase rate of the 2-, 4- and 8-nm-period layered films is almost zero at a 1, 2, and 4 nm wear depths, respectively. This wear depth corresponds to the thickness of the interface of each carbon nitride [C-N] and boron nitride [B-N] layer. At both edges of the wear scar, short steps of layered depth were observed in the half-thickness of each period-layered film. These results indicate that the wear resistance increased because of the prevention of fracture growth at the interface between B-N and C-N layers in the case of multilayered films. To realize single-layer processing, the processing properties dependencies of the load and sliding cycles were evaluated. Under suitable conditions, the processed depth corresponds to the depth of each C-N and B-N layer. As a practical application of this newly developed fabrication technique, three-dimensional nanometer-scale profiles, such as 300 nm × 300 nm square, lines and spaces with 100 nm periods and three-step grooves were fabricated.

The influence of the particle size of fillers on the frictional wear properties of dental composite resins has been investigated. Five kinds of silica fillers with mean particle sizes of 0.5, 3.3, 4.3, 7.9, and 15.5 μm are used in this study. The filler volume is kept constant at 70 wt%. The coefficient of friction between the abrasive and the specimen was determined by a frictional wear device employing a rotating wheel. After the test, the wear depth was measured by a surface profilometer and the wear surface was observed by FE-SEM. The results demonstrate that the coefficient of friction and the wear depth increase with an increase in the particle size of the filler of composite resins. In addition, a linear correlation between the coefficient of friction and wear depth was found.

The corrosion performance provided by two anodizing treatments aiming at obtaining films with comparable thickness but different pore morphology was evaluated by immersion, salt spray, and a hybrid tests. The hybrid test was performed in cycles by alternating between immersion and salt spray tests. The corrosion progression was evaluated at selected times by electrochemical impedance spectroscopy (EIS). The EIS indicated that, during immersion test, the self-sealing of the pores due to the precipitation of aluminium hydroxide was favored, and it provided a substantial contribution to the improved corrosion resistance. Vice versa, during salt spray testing, the continuous flow of electrolyte promoted aluminium oxide film dissolution. The EIS study was complemented by the surface appearance and composition of specimens before and after exposure using Field Emission-Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray (EDX) analysis. Overall, the relative performance of the anodic oxides was shown to be dependent on the exposure conditions. In fact, an anodic film with finer pores behaved better during immersion tests, whereas films with coarser pores provided better corrosion protection during salt spray testing.

Degradation of fluorinated polyurethane coating under UVA and salt spray. Part I: Corrosion resistance and morphology

Low-cost manufacturing in the electronics industry is becoming more demanding, particularly in the production of consumer electronics. Such manufacturing processes require reliable and low-cost lead-free solders. Among the low-temperature lead-free solders, eutectic Sn-Bi solder attracts a great deal of interest as it offers good reliability compared with that of Sn-Pb solders. In this paper, the reliability of eutectic 42%Sn-58%Bi (wt.%) lead-free solder is studied using combinations of environmental tests such as thermal aging (TA) at 100 °C, salt spray test (SST), and a sequential combination of TA and SST. Microstructural studies on the samples are performed at different time intervals. To study the effect of salt spray and TA on the mechanical reliability, drop testing is performed on the samples. Failure analysis is conducted after different tests. Marked corrosion is seen after the SST. This also has a considerable effect on the impact strength of the solder interconnections. TA increases the thickness of the intermetallic layers, which is found to affect the drop performance.

Self-piercing riveted (SPR) joints in automobiles inevitably suffer from corrosion damage and performance reduction. In this work, the influence of salt spray corrosion on the mechanical properties of TA1-Al5052 alloy SPR joints was studied. The TA1-5052 SPR joints were prepared and salt spray tests were carried out for different durations. The static and fatigue strengths of the joints after salt spray corrosion were tested to analyze the effect of salt spray duration on the performance of the joints. The results show that the joints’ static strength and fatigue strength decrease with prolonged salt spray time. The salt spray duration affects the joint’s tensile failure mode. The tensile failure without corrosion and with a short salt spray time is the fracture failure of the lower aluminum sheet, and the tensile failure of the joints after a long time of salt spray corrosion is the failure of the rivets. The fatigue failure form of the SPR joint is the formation of fatigue cracks in the lower aluminum sheet, and salt spray time has little effect on the fatigue failure form. Salt spray corrosion can promote the initiation and propagation of fatigue cracks. The fatigue crack initiation area is located at the boundary between the lower aluminum sheet and the rivet leg. The initiation of cracks originates from the wear zones among the sheet metal, rivets, and salt spray particles.

Characterization of silicon-based chromium (VI) replacement coatings by using time-of-flight secondary ion mass spectrometry and salt spray tests

On the commensuration of plastic plowing at the microscale