Mean Depth Of Erosion Research Articles

Enhancement of cavitation erosion resistance of 316 L stainless steel by adding molybdenum

The influence of Mo on ultrasonic cavitation erosion of 316 L stainless steel in 3.5% NaCl solution were investigated using an ultrasonic cavitation erosion (CE) facility. The morphologies of specimen after cavitation erosion were observed by scanning electron microscopy (SEM). The results showed that the addition of Mo can sharply decrease the mean depth of erosion (MDE) of 316 L SS, implying the increased resistance of cavitation erosion. In order to better understanding the influence of Mo on the cavitation erosion of 316 L SS, the semi-conductive property of passive films on 316 L SS containing different concentrations of Mo were studied by Mott-Schottky plot. Based on Mott-Schottky results and semiconductor physics, a physical model was proposed to explain the effect mechanism of Mo on cavitation erosion of 316 L SS.

Cavitation erosion of plasma-sprayed CoMoCrSi coatings

CoMoCrSi coatings were manufactured on a steel substrate by atmospheric plasma spraying (APS), followed by a three-hour heat treatment at a temperature of 800°C and 1000°C, respectively. Prior to the ultrasonic test of the cavitation erosion, coating cross-sections were observed by scanning electron microscopy (SEM) and analyzed by X-ray diffraction (XRD). 3D profiles were employed to investigate the erosion mechanism on both pristine and eroded surfaces. As a result, it is shown that the heat treatment can significantly reduce the mean erosion depth of the CoMoCrSi coatings and the cavitation damages mainly consist of the removal of the splashes with weak adhesion during plasma spray and the delamination of fragments from bubble collapses.

Mechanical Hardening and Resistance to Cavitation Erosion of the Austenitic Stainless Steels with Varying Proportions of Delta Ferrite

The paper analyzes, comparative, the resistance to the cavitation erosion for the X5CrNi18-10 classic steel, with that provided by two another steels, processed experimental, with approx. 0.1 % C, 24% Cr, 18 % , approx. 10% Ni and wich was mechanically hardened by vibro rolling. Cavitation tests were performed on a vibrating device with piezoelectric crystal, in the Laboratory of Hydraulic Machines in Timisoara ( LMHT ), determining the characteristic curves of the variation in time of the mean depth erosion, MDE (t ) and mean depth erosion rate, MDER (t). By mechanical tests and by metallographic investigation is warranted increased erosion resistance after cold plastic deformation and minimization the effect of reduction its to higher proportions of delta ferrite , due to higher chromium content. Conclusions detached, after the investigations, serve designers and processors by stainless steel to chemical composition optimization and to manufacturing processes, in order to increase the lifetime of hydromechanical equipment, such as hydraulic turbines, pumps and throttle butterfly valves on pipelines forced, etc.Keywords: mechanical hardening, characteristic curves, resistance to cavitation, microstructure, chemical elements, mechanical properties

Quantification of B2 glenoid morphology in total shoulder arthroplasty

B2 glenoid morphology is challenging to address with shoulder reconstruction. Deformity often renders current techniques inadequate, necessitating compromises that limit long-term implant durability. The purpose of this study was to perform in vivo measurements of glenoid deformity to better appreciate the orientation of the B2 biconcavity demarcation and erosion that surgeons face intraoperatively. A consecutive 106 total shoulder arthroplasty cases for primary glenohumeral osteoarthritis were studied. We classified glenoids by direct visualization and noted lines of biconcavity demarcation and erosion in B2s. We then calculated the "angle of erosion" as that between the back side of the unsupported, smooth-backed glenoid sizer disk and the neoglenoid. We obtained depth measurements throughout the reaming process and monitored subchondral bone. We classified 43 of 106 glenoids (41%) as B2. A biconcavity demarcation line between the paleoglenoid and the neoglenoid was present, on average, from the 1-o'clock to the 7-o'clock position for a left shoulder. Mean depth of erosion was 4.4 mm, occurring at 114° on a Cartesian coordinate system for a left shoulder. The mean angle of erosion was 18° (range, 8°-43°). Despite reaming, 20 of 43 B2 glenoids (47%) had incompletely supported components at final seating. Arthritic B2 glenoids are common, and their maximal erosion is usually posteroinferior. Use of standard glenoid components to reconstruct them may require significant subchondral bone removal to achieve complete bone support. Alternatively, as a compromise, maintenance of subchondral bone in these cases requires implanting components with incomplete bony support.

Microstructural Phenomena Occurring during Early Stages of Cavitation Erosion of Al-Si Aluminium Casting Alloys

The researches have concerned cavitation erosion of AlSi7Mg and AlSi11Mg aluminium casting alloys. The alloys have been investigated in the as-cast condition and after the precipitation hardening. The cavitation erosion tests were performed using vibratory cavitation erosion equipment in 5 minutes. Resistance to cavitation of tested materials was estimated by means of MDE (mean depth of erosion) parameter according to ASTM G32. After the cavitation tests eroded surface of the specimens has been observed by means of scanning electron microscopy. The roughness of the surface was measured on profile contact tester. The best resistance for cavitation erosion exhibited AlSi7Mg alloy after heat treatment, the weakest AlSi11Mg alloy in as-cast condition.

Ultrasonic cavitation erosion of nodular cast iron with ferrite–pearlite microstructure

The cavitation erosion of ductile cast iron with ferrite–pearlite microstructure was analyzed based on ultrasonic experiments performed according to ASTM G32-2010 and the resistance was compared to the C45 steel with similar hardness. The microstructural observation of the surface for different exposure times to the ultrasonic cavitation reveals the fact that the process initiates at the nodular graphite–ferrite interface and is controlled by micro-galvanic activities and mechanical factors. The cavitation erosion resistance was evaluated based on the evolution of the mean depth erosion and the mean depth erosion rate as a function of the cavitation time. The cavitation erosion rate of the cast iron is up to 1.32 times higher than the one of the C 45 steel with similar hardness. This is explained by the occurrence of stress concentrators due to the expulsion of the graphite from the metallic matrix.

Vibratory Cavitation Erosion With Vibrating and Stationary Specimens

AbstractIn the framework of the International Cavitation Erosion Test (ICET), 119 vibratory cavitation erosion tests were performed. Seventy of these tests were with vibrating specimens (VRV), and forty-nine with stationary specimens (VRS). From these tests, twenty tests of each type were chosen for this study. VRV tests are covered by ASTM G32-10, whereas for VRS, no standard has yet been published. This anomaly stems from the difficulties encountered in both testing and evaluating of VRS tests. All forty cavitation erosion–time curves were analyzed by the Transient Response for Erosion (TRE) method. For each curve, all three parameters were determined, namely: time lag (TL), time constant (τ), and the asymptotic value of the mean depth of erosion, mean depth of erosion (MDE) MDEMAX. These parameters were further applied to calculate the scatter of test results as obtained from various specimens tested under identical conditions. This method enables the determination of the absolute and relative scatter values at any time value along the test. Finally, several guidelines are specified for preparation of a future VRS standard.

Cavitation erosion behavior of Hastelloy C-276 nickel-based alloy

The cavitation erosion behavior of Hastelloy C-276 alloy was investigated using an ultrasonic vibratory apparatus and compared with that of 316L stainless steel. The mean depth of erosion (MDE) and erosion rate (ER) curves vs. test time were attained for Hastelloy C-276 alloy. Morphology and microstructure evolution of the eroded surface were observed by scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) and the predominant erosion mechanism was also discussed. The results show that the MDE is about 1/6 times lower than that of the stainless steel after 9h of testing. The incubation period of Hastelloy C-276 alloy is about 3 times longer than that of 316L stainless steel. The cavitation-induced nanometer-scaled precipitates were found in the local zones of the eroded surface for Hastelloy C-276. The selective cavitation erosion was found in Hastelloy C-276 alloy. The formation of nanometer-scaled precipitates in the eroded surface may play a significant role in the cavitation erosion resistance of Hastelloy C-276.

Improvement in cavitation erosion resistance of AISI 316L stainless steel by friction stir processing

Commercial AISI 316L plates with the initial grain size of 14.8 μm were friction stir processed (FSP) with different processing parameters, resulting in two fine-grained microstructures with the grain sizes of 4.6 and 1.7 μm. The cavitation erosion behavior, before and after FSP, was evaluated in terms of incubation time, cumulative mass loss and mean depth of erosion. A separate cavitation erosion test was performed on the transverse cross section of a FSP sample to reveal the effect of grain structure. It was observed that FSP samples, depending on their grain size, are at least 3–6 times more resistant than the base material against cavitation erosion. The improvement in cavitation erosion resistance is attributed to smaller grain structure, lower fraction of twin boundaries, and favorable crystallographic orientation of grains in FSP samples. The finer the grain size, the more cavitation erosion resistance was achieved. Moreover, the microstructures of eroded surfaces were studied using a scanning electron microscope equipped with EBSD, and an atomic force microscope. The mechanisms controlling the cavitation erosion damage in friction stir processed AISI 316L are also discussed.

Evaluation of Fifty-Two Cavitation Erosion Tunnel Tests

AbstractIn the framework of the International Cavitation Erosion Test (ICET), 52 cavitation erosion tests were performed in cavitation tunnels. These tests were performed by six labs in eight test groups, on five metallic reference materials. The subjects studied are: cavitation erosion trail, test specimen, calculation of mean depth of erosion (MDE), values, cavitation erosion–time curves, measuring accuracy, variation of test results, and material classification. In all these categories, deficiencies were detected such as: lack of data on eroded areas, water flow velocity at the specimen’s surface, and an evaluation misconception based on the assumption that the eroded area is equal to the specimen area. These deficiencies cast heavy doubt on the reliability of the test results. Only eighteen tests were found relevant for obtaining quantitative data. Recommendations are made to overcome some of the detected deficiencies and to improve both reliability and applicability of future cavitation erosion tunnel test results.

Role of arginine and fluoride in the prevention of eroded enamel: anin vitromodel

The aim of this study was to investigate the effect of arginine and fluoride on the reduction of erosive wear. Bovine enamel blocks were randomly allocated into four groups (n=20) and exposed to: ESPR group (8% arginine, 1450ppm sodium monofluorophosphate, calcium carbonate and titanium dioxide); ESen group (1450ppm sodium monofluorophosphate, 5% potassium citrate); positive control PC group (1500ppm sodium monofluorophosphate) and negative control NC group (water). The samples were submitted to six alternating cycles of demineralization-remineralization (cola, 10minutes; artificial saliva, 1hour, respectively). Before and between cyclic demineralization and remineralization, blocks were treated with slurries of the respective toothpastes or water (1minute). Erosive tissue loss was analysed by microhardness and profilometry. Data were analysed by ANOVA and Tukey tests for individual comparisons among the groups (p<0.05). In microhardness, the ESPR (217.46±55.45) group was significantly better than the other treatment groups (PC = 302.76±96.10; ESen = 315.56±74.56; p<0.001). The ESPR group showed a similar loss to NC group (NC = 210.8±49.98; p=0.991). The mean erosion depth (+/- SE, μm) was detected between NC (14.37±1.72) and dentifrices tested (ESPR (4.11±1.34), ESen group (7.64±1.61) and PC (8.20±2.19) (p=0.000). From the results of the present study, the effectiveness of Sensitive Pro Relief in the prevention of erosive surface loss seems to be attributed to the possible effect of the arginine associated with fluoride.

Characteristics of Cavitation Erosion Using Image Processing Techniques

This paper deals with the analysis of eroded surfaces obtained from cavitation-erosion experiments on stainless steel in water and oil-in-water (o/w) emulsions using image processing. Two analysis techniques that are very promising in this respect are the wavelet decomposition transform and fractals. These can be used to extract parameters that characterize the cavitation intensity in a similar manner to that of the mean depth of erosion (MDP). The extracted parameters are the wavelet energy and entropy as well as the fractal dimension. Both of the image feature parameters and the MDP decrease with adding oil to water. Also, it was found that the variation of image feature parameters versus concentration of oil-in-water emulsions has a general trend that does not depend on magnification factor. The cavitation erosion behavior and mechanism for water and o/w emulsions were analyzed and it was found that the predominant failure mode was fatigue for water and o/w emulsions. The results show that a corrosive effect appears at 5 and 10 wt% o/w emulsions.

Scaling of cavitation erosion progression with cavitation intensity and cavitation source

A simple mathematical expression is presented to describe cavitation mean depth of erosion versus time for cavitating jets and ultrasonic cavitation. Following normalization with a characteristic time, t*, which occurs at 75% of the time of maximum rate of erosion, and a corresponding material characteristic mean erosion depth, h*, the normalized erosion depth is related to the normalized time by h¯=1−e−t¯2+e−1t¯1.2. This was obtained by conducting systematic erosion progression tests on several materials and varying erosion field intensities. Both a modified ASTM-G32 method and Dynaflow's cavitating jets techniques were used and the jet pressures were varied between 1000 and 7000psi. The characteristic parameters were obtained for the different configurations and the correlation was found to be very good, exceeding an R2 of 0.988 for all cases. Relationships between these parameters and the jet pressure were obtained and resemble familiar trends presented in the literature for mass loss. The study allowed a comparative evaluation and ranking of the various materials with the two accelerated erosion testing methods used. While several materials ranked the same way with the different erosion intensities and testing method, the relative ranking of erosion resistance of some materials was seen to be dependent on the cavitation intensity.

Preventive effects of dentifrice containing 5000 ppm fluoride against dental erosion in situ

Objective To evaluate the effectiveness of a dentifrice with 5000 ppm fluoride in preventing dental erosion by orange juice in situ in comparison to a control dentifrice with 1450 ppm fluoride. Methods This was a double-blind and randomized clinical study with a cross-over design. Sixteen subjects wore an intra-oral appliance containing two enamel disks with an exposed surface of approximately 2 mm × 5 mm. Enamel disks in the study group were treated with a dentifrice with 5000 ppm fluoride and in the control group with 1450 ppm fluoride. The subjects rinsed with slurries of study dentifrices for one minute before immersing the enamel disks in 250 ml orange Juice four times in an 8-h period daily. The treatment procedure was repeated for three 5-day phases for each dentifrice. Enamel erosion was measured after each 5-day treatment phase using a focus-variation 3D scanning microscopy. Medians and inter-quartile ranges (IQR) of mean erosion depth were compared between the groups. Results The mean erosion depths of enamel varied greatly amongst the subjects. Enamel treated with 5000 ppm fluoride had less erosion (median 5.7 μm, IQR 4.5 μm) as compared to the control (median 12.6 μm, IQR 12.3 μm) after 15 days of fluoride treatment and erosive challenge cycles ( p < 0.05). Conclusions Enamel treated with 5000 ppm fluoride had significantly improved resistance to erosion by orange juice. Periodic application of 5000 ppm fluoride may be beneficial in individuals at risk of acidic erosion associated with soft drink consumptions.

Measurement by vertical scanning profilometry of resorption volume and lacunae depth caused by osteoclasts on dentine slices

The resorption pit assay is classically used to evaluate osteoclast activity on bone or dentine slices that can be eroded by these cells. Two different types of cells were generated from peripheral blood mononuclear cells cultured in the presence of M-CSF + sRANKL or with M-CSF + LPS. At the end of the culture period (21 days), cells were discarded and the dentine slices stained with toluidine blue and examined with an NT9100 Wyco vertical scanning profilometer. The images of the dentine surface were corrected for tilt and the eroded volume was calculated on the whole images. The depth of the eroded pits was determined. The data files were used to reconstruct the surface of the slices by standardizing the ground level to compare both conditions. Osteoclasts generated with M-CSF + sRANKL were capable of resorbing a more important volume than those generated with M-CSF + LPS. In addition, the formers were able to resorb the dentine matrix more deeply. Data provided by the microscope were used to reconstruct three-dimensional images of the dentine slices with pseudo colours varying with the depth of erosion. Vertical scanning profilometry, a technique used to measure the roughness of polished or etched surfaces in metallurgic industry, can be used to accurately measure the eroded volume and the mean erosion depth done by osteoclasts in the resorption pit assay.

Ranking of Materials’ Erosion Resistance and of Erosion Test Methods’ Intensity by the Transient Response Method

Abstract Modeling of cumulative erosion-time curves by the transient response method is based on the response curve of first-order servo systems to a step input. According to this model, it is possible to accurately model erosion-time curves by means of three parameters: Maximal erosion level, MDEF (MDE denotes mean depth of erosion) (μm), time constant, τ (h), and time lag (h). This method is adequate for ranking of materials by their erosion resistance and ranking of erosion test methods by their intensity. These rankings are performed for five metallic reference materials and seven erosion test methods for 22 erosion tests.

Experimental comparison of cavitation erosion rates of different steels used in hydraulic turbines

The prediction of cavitation erosion rates has an important role in order to evaluate the exact life of components in fluid machineries. Hydro-Québec has studied this phenomenon for several years, in particular in hydraulic turbine runners, to try to understand the different degradation mechanisms related to this phenomenon. This paper presents part of this work. In this study, we carried out experimental erosion tests to compare different steels used in actual hydraulic turbine runners (carbon steels, austenitic and martensitic stainless steels) to high strength steels in terms of cavitation erosion resistance. The results for these different classes of steels are presented. The tests have been performed in a cavitating liquid jet apparatus according to the ASTM G134-95 standard to simulate the flow conditions. The mass loss has been followed during the exposure time. The maximum depth of erosion, the mean depth of erosion, and the mean depth erosion rate are determined. As a result we found that ASTM-A514 high strength steels present excellent cavitation erosion resistance properties. The cavitation eroded surface is followed by optical profilometry technique. Determination of mechanical properties and examinations of the eroded surfaces of the samples have also been carried out in order to identify the erosion mechanisms involved in the degradation of these kinds of materials.

Preventive Effect of Commercial Desensitizing Toothpastes on Bovine Enamel Erosion in vitro

This study evaluated in vitro commercial desensitizing toothpastes with respect to the prevention of erosion and explored the effect of their agents alone or in combination with fluoride. Bovine enamel blocks were randomly allocated to five groups of 20 and exposed to: Sensodyne ProNamel (1,425 ppm F as NaF, 5% KNO₃), Sensodyne Original (no fluoride, 10% SrCl₂), Colgate Sensitive (1,450 ppm F as sodium monofluorophosphate, 5% K citrate), Crest (fluoride-only toothpaste, 1,100 ppm F as NaF) and water (negative control). A second experiment was conducted with experimental dentifrices containing fluoride (NaF, 1,100 ppm F), 10% SrCl₂, 5% KNO₃or 5% K citrate alone or the latter three combined with F. The samples were submitted to four cycles, alternating demineralization (cola, 10 min) and remineralization (artificial saliva, 1 h). Before and between cyclic de- and remineralization, blocks were treated with slurries of the respective toothpastes or water (1 min). Erosive tissue loss was analyzed by profilometry. Data were analyzed by Kruskal-Wallis and Dunn’s tests (p < 0.05). The mean erosion depth (± SE, µm) was significantly less for Colgate Sensitive (0.04 ± 0.00), Sensodyne Original (0.06 ± 0.01) and Crest (0.07 ± 0.01) than for Sensodyne ProNamel (2.36 ± 0.25) or water (2.92 ± 0.24), which did not significantly differ from each other. Both F and the desensitizing agents alone reduced erosion, but no additive effect was found. In addition, the combination of F and KNO₃ did not reduce erosion. These in vitro results suggest that the presence of fluoride or desensitizing substances in toothpastes, alone or in combination, can reduce erosion of enamel, but this is not valid for all the formulations.

Cavitation Erosion of 6061 Aluminum Alloy Coated with TiAlN Thin Film

Cavitation erosion is one of the major problems to be solved in hydraulic machinery. Propellers of high speed boats require a light weight metallic material for their improved high performance. This example tells us that solutions are the developments of way for the improvement of cavitation erosion resistance of light weight metallic material. Coatings on aluminum alloy can enhance the cavitation erosion resistance. This study discussed the cavitation erosion behavior of 6061 aluminum alloy coated with TiAlN thin film. TiAlN coatings were deposited by DC magnetron sputtering method at various nitrogen partial pressures of the coating process using Ti based alloy cathode. The composition of target material was 90wt%Ti, 6wt%Al and 4wt%V. Using the TiAlN coated 6061 aluminum alloy specimen, cavitation erosion tests were carried out to investigate its resistance to the ultrasonic cavitation erosion. Prior to and after the tests, the specimen surfaces were analyzed by using the surface analysis techniques such as micro-hardness test, AFM, SEM, GXRD and scratch test to measure the microstructure of thin film and bonding properties of the applied TiAlN coatings to the substrate material. An improvement in cavitation erosion resistance could be seen with TiAlN coating on 6061 aluminum alloy. Especially, the coating at a nitrogen flow rate of 0.85 sccm or more were very effective in reducing the surface cavitation erosion from the ultrasonic cavitation. In the observation of surface damages during the cavitation erosion tests, the surface cracks in TiAlN were created by the bending of TiAlN coating which were resulted from the plastic deformation of the soft substrate material of aluminum alloy. Once the cracks initiate, drastic delaminations of TiAlN from the substrate material occured. The mean depth erosion rate (MDER) could be evaluated by critical and delamination loads measured by scratch test.

Logistic curve model of cavitation erosion progress in metallic materials

The authors previously found that the change in volume loss rate with the exposure time can be expressed by a logistic curve. In this study, the validity of this model is examined for various materials such as pure aluminum, carbon steels, stainless steels, cobalt alloys, and so on. The MDE (mean depth of erosion) d as a function of the exposure time can be expressed by three parameters α , β and c as in the following equation: d = α β t − 1 β ln 1 + c 1 + c e − α t The parameters α , β and c are derived from the relation between the nominal incubation period and the slope of the maximum rate stage, from the average thickness of the removed layer when the nominal incubation period is terminated, and from an arbitrary point ( t 0 , d 0 ) of the MDE in the maximum rate stage. We conclude that the calculated curve based on this model is in good agreement with the MDE data points for various materials, test conditions and test methods.