Deformation and fracture of single-crystal and sintered polycrystalline silicon carbide produced by cavitation

An investigation was conducted to examine the deformation and fracture behavior of single-crystal and sintered polycrystalline SiC surfaces exposed to cavitation. Cavitation erosion experiments were conducted in distilled water at 25 C by using a magnetostrictive oscillator in close proximity (1 mm) to the surface of SiC. The horn frequency was 20 kHz, and the double amplitude of the vibrating disk was 50 microns. The results of the investigation indicate that the SiC (0001) surface could be deformed in a plastic manner during cavitation. Dislocation etch pits were formed when the surface was chemically etched. The number of defects, including dislocations in the SiC (0001) surface, increased with increasing exposure time to cavitation. The presence of intrinsic defects such as voids in the surficial layers of the sintered polycrystalline SiC determined the zones at which fractured grains and fracture pits (pores) were generated. Single-crystal SiC had superior erosion resistance to that of sintered polycrystalline SiC

Combination Effect of Corrosion Inhibitors of Na2CrO4 and Na2HPO4 for Mild Steel in 3% NaCl Solution

The combination effects of inhibitor of Na2CrO4 and Na2HPO4 in 3% NaCl solution for 0.15% carbon steel were studied by weight loss tests during ten days and electrochemical tests. Na2CrO4 prevents the initiation of deep pits. Na2HPO4 protects most of the steel surface from the general corrosion attack but produces localized deep pits. v-7hen Na2CrO~ and Na2HPO4 are added together into 3% NaCl, icorr. becomes smaller than that for each inhibitor. Especially, adding 10 ppm Na2CrO4, i corr. is almost the same regardless of the concentration of Na2HPO4 (10-100 ppm) . The combination of Na2CrO4 and Na2HPO4 stifles the disadvantage of individual inhibitor and thus provides much effective prevention of corrosion in sufficient concentration

Effect of temperature on the cavitation erosion of cast iron

Vibratory cavitation erosion tests of gray cast iron, together with tests of tool steel and 316 stainless steel for comparison, were performed at various water temperatures and horn amplitudes under a suppression pressure of 1 bar. The erosion processes for cast iron under the highest temperatures used (200 and 230 [deg]F, i.e. 93 and 110 [deg]C) are similar to those at room temperature. For each of the materials tested, the maximum weight loss rate increases, shows a peak and then decreases with increasing temperature. However, the maximum damage temperature for cast iron decreases with amplitude, i.e. 200, 170 and 160 [deg]F (93, 77 and 71 [deg]C) for double-horn amplitudes of 1.0 x 10-3, 1.38 x 10-3 and 1.78 x 10-3 in (25.4, 35.1 and 45.2 [mu]m). The peak for tool steel and 316 stainless steel occurs at 160 [deg]F (71 [deg]C) regardless of amplitude. Liquid temperature effects for cast iron erosion were explained by considering the interrelation between corrosive action and mechanical action due to cavitation bubble collapse.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25276/1/0000719.pd

Effects of applied stress on cavitation erosion

Cavitation erosion under static applied stress and/or alternating stress was studied using steel specimens which were set in close proximity to an oscillating horn in ion-exchanged water. For increasing static applied tensile or compressive stress, weight loss and its rate do not vary in a monotonic fashion but first decrease, then increase through a peak, and then decrease again. Tensile stress except for given stress regimes, and compressive stress at all stress levels, decreases erosion damage compared with zero-stress values. Under alternating stress, the weight loss rate varies with trends similar to those under static applied stress. However, the weight loss rate is larger than for the same static stress, so that the erosion damage is more affected by alternating stress than by static stress. The behaviors under applied stress are discussed through the effect of stress on the erosion particles.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23926/1/0000171.pd

An application of bubble collapse pulse height spectra to venturi cavitation erosion of 1100-o aluminum

Venturi cavitation erosion tests were performed and correlated with bubble collapse pulse height spectra measured by a microtransducer. The effects of the throat velocity and the cavitation number [sigma] (referred to the downstream pressure and throat velocity) on the erosion rate (MDPR) were studied. The velocity damage exponent was 4.11 for 0.62 [les] [sigma] [les] 0.80, while the MDPR is almost independent of velocity for [sigma] = 0.85. The MDPR decreases with increased [sigma] for 0.62 [les] [sigma] [les] 0.85. The data were reduced to "acoustic power" (from pulse height spectra) and "erosion power" (the ultimate resilience multiplied by the MDPR). A near-linear relationship was found between these. Their reciprocal ratio [eta]cav [approximate] 7 x 10-11. For [sigma] = 0.62, the data deviated from the others, possibly because of the work hardening of the eroded surface.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25661/1/0000213.pd

Erosion Between Two Curved Surface Oscillating at Close Proximity in Liquid

In the previous paper，the erosion damages have been discussed by using on two parallel surfaces oscillating at close proximity in liquid. In the present paper，further erosion tests are carried out on the curved surfaces which are frequent1y found in machine elements. In this test conditions，the shearing force of squeezed film becomes very small，and the damages are mainly caused by the collapse pressure of cavitation bubbles. The cavitation bubble moves due to the flow of liquid film in the radial direction and no fixed-type cavitation appears at the small film thickness. Accordingly，t he distribution of damage in the radial direction of the spherical disc depends on the minimum fi1m thickness and also on the curvature of disc

A Study of Washing of Fabrics by Cavitation Bubble Collapse Pressures

Washing of fabrics by cavitation bubble collapse pressures was studied using a magnetostrictive vibratory device. The process of removing Fe203 soil particles attached on nylon cloth was observed with the naked eye and by a scanning electron microscope. When the fabrics were exposed to cavitation bubble collapse pressures only for 2 minutes， the percentage of soil removal was more than 90%， which was extremely high compared with those obtained by the ordinary washing procedure such as the laundry tester and the commercial ultrasonic cleaning device. Thus， we found that the application of cavitation bubble collapse pressures in the washing of fabrics may be useful

Cavitation erosion in vibratory and venturi facilities

Water cavitation erosion results from Venturi and vibratory tests of fully annealed commercially pure aluminum and annealed carbon steel are compared to obtain a better understanding of the mechanisms involved in these static and flowing tests. Significant differences between the initial pit characteristics were found, which were due primarily to the different bubble sizes and collapse pressures. The ratio of erosion rates from the two facilities was larger for the weaker material (aluminum). Results were also compared with pulse height spectra from individual bubble collapse in the Venturi tests.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24351/1/0000619.pd

Influence of cavitation erosion on corrosion fatigue and effects of resistance to that influence by the surface coatings

http://deepblue.lib.umich.edu/bitstream/2027.42/6887/5/bad0467.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/6887/4/bad0467.0001.001.tx