A. Abouel-Kasem

Investigation Into Cavitation Erosion Pits

Cavitation erosion pits and their effects on erosion progression were investigated in detail for SUS 304 stainless steel, α + β brass (60/40), and pure aluminum (Al-99.999 and Al-99.92) by means of vibratory erosion. Two kinds of erosion pits were found on the specimen surfaces, one by microjet impact and the other by shockwave blow. Systematic observations of the feature of microjet-pits with the testing time showed that the sizes and shapes of microjet-pits did not change at all and such pits scarcely played an important role in developing the erosion. Moreover, the feature morphology of eroded surfaces, and dislodged particles and their large sizes revealed that microjet-pits had a limited effect on erosion and that the predominant failure was a fatigue process.

Design and Performance of Slurry Erosion Tester

A slurry whirling arm erosion test ring was constructed and a series of erosion tests andpost-erosion analysis were carried out using a paint erosion indication technique. Thepattern of the paint removal presented a highly visual and accelerated map for theerosion process and its behavior. Also, the erosion rate of paint removal was investigatedunder a number of erosion variables. It was observed that the rebounding of the erodentparticles from the sample surface play an important role in developing erosion for thistester. The erosion pattern showed that the effect of the rebound particles depends on theimpact velocity and impingement angle. It was also observed that the erosion behavior ofpaint as a function of impingement angle, impact velocity, and erosion time was similarto that reported in literature for engineering materials. The slurry whirling arm erosiontester seems to be promising for simulating the slurry process in real cases.

Cavitation Erosion Mechanism Based on Analysis of Erosion Particles

The mechanism of cavitation erosion is investigated in detail through observations of the removed particles from pure aluminum (Al-99.999). The particles removed during the incubation stage have distinctive characteristics compared to those removed in the subsequent stages. These characteristics are distinguished by lamellae structure, foldness, waviness, large size as well as one of the particle surfaces appeared to be part of the original face of the specimen. Therefore, these characteristics can be used as a monitor for early detection of cavitation erosion in closed systems. Systematic observations of disloged particles and eroded surface morphology show that the dominant failure mode in cavitation erosion is fatigue.

Particle Size Effects on Slurry Erosion of 5117 steels

The effect of particles size and shape on erosion rates and erosion mechanisms of 5117 steels are investigated using slurry whirling-arm ring. Six different sized silica sand particles are used as erodent. These particles are characterized in terms of their average diameter, aspect ratio, and circularity factor. The measured average diameter varies from 112.7 μm to 516.4 μm. The wear tests are carried out at impact velocity of 15 m/s and 30 deg and 90 deg impact angles using a sand-water mixture of 1 wt % concentration. Analysis of erosion rates shows that there exists threshold energy of impacting particles at which a transition in erosion rate is noticed for sizes of 200 μm. It is also observed that the erosion rate increases with the increase in shape factors (aspect ratio and circularity factor). The surface morphology of the eroded surface at impact of 30 deg shows that below 200 μm, the erosion mechanism is indentation and material extrusion and above 200 μm, the erosion mechanism is ploughing.

Investigation of Temperature Effects on Cavitation Erosion Behavior Based on Analysis of Erosion Particles

The effect of temperature on the wear particles produced by vibratory cavitation erosion tests on Al-99.92 in distilled water was analyzed. Scanning electron microscope images of wear particles were obtained, forming a database for further analysis. This study showed that the variation of average particle size with temperature was very much similar to the variation of weight loss with temperature. The average particle size was maximum at 40°C. It was also observed that the average particle size was time dependent. The particles morphology features revealed that the predominant erosion mechanism was fatigue failure, irrespective of the temperature.

Quantitative Analysis of Cavitation Erosion Particle Morphology in Dilute Emulsions

Wear particles produced by vibratory cavitation erosion tests on 1017 carbon steels in water and oil-in-water (o/w) emulsions were analyzed. Scanning electron microscope (SEM) images of wear particles were acquired, forming a database for further analysis. The particle morphology features were first clarified. Next, the size parameters (size, area, and perimeter) arul shape factors (elongation and roundness) were determined for each test liquid, using image analysis software. The size parameters of the removed particles were higher in water than in o/w emulsions. While the shape factors could not significantly discriminate between the particles produced in water and o/w emulsions. The size distribution was in a wide range for water than that for o/w emulsions. The cavitation erosion mechanism is fatigue failure for water and o/w emulsions.

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.

Effect of Impact Angle on Slurry Erosion Behavior and Mechanisms of Carburized AISI 5117 Steel

The paper reports a study of slurry erosion of carburized AISI 5117 steel using whirling-arm rig. The study is mainly focused on studying the erosion wear resistance properties of AISI 5117 steel after carburizing at different impact angles. The mechanisms of erosion wear at different impact angles are presented using SEM examination of eroded samples. In addition, the SEM images of eroded samples at different stages are presented for better understanding of erosion mechanisms at different angles. The tests were carried out with particle concentration of 1 wt %, and the impact velocity of slurry stream was 15 m/s. Silica sand having a nominal size range of 250 – 355 μm was used as an erodent. The results showed that, carburizing process of steel increased the erosion resistance and hardness compared with untreated material for all impact angles. The erosion resistance of AISI 5117 steel increases by 70, 57, 60 and 36 % at an impact angle of 30o, 45o, 60o and 90o, respectively as result of carburizing, i.e. the effectiveness of carburizing was the highest at low impact angles. Treated and untreated specimens behave as ductile material, and the maximum mass loss appears at impact angle of 45 o . Plough grooves and cutting lips appears for acute impact angle, but the material extrusions are for normal impact angles. The erosion traces are wider and deeper for untreated specimens comparing by the shallower and superficial ones for the carburized specimens.

Rubber-Filler Interactions and Its Effect in Rheological and Mechanical Properties of Filled Compounds

This paper will set out a brief review of the needs, early development, and current status of the nature of the interactions between rubber matrix and particulate filler and the intrinsic effect on mechanical and rheological behavior of filled vulcanizates. Fillers are commonly added to commercial elastomers for reasons of economy and also to favourably modify properties such as stiffness, tensile strength, heat distortion, mouldability, and other important properties, such as impact properties and elongation to break. The behavior of elastomers reinforcing with certain fillers like carbon black or high-structure silica need to be understood deeply to clarify the rubber-filler interaction and its effect on rheological and mechanical properties of filled rubber compounds. In this paper the nature of interaction between the elastomer and filler particles, the types of reinforcing fillers, the effect of its size and structure, the reinforcing concepts, and the mechanical properties of filled rubber are discussed.

Effect of Surface Properties Modification on Slurry Erosion–Corrosion Resistance of AISI 5117 Steel

The erosion–corrosion (E–C) wear behaviors of electroless nickel phosphorus (Ni-P) coating, carburizing and untreated low alloy steel AISI 5117 in water–sand slurry and saline–sand slurry were investigated using whirling-arm tester. The E–C wear mass loss was measured to evaluate the effect of mediums and surface modifications. The microstructure of carburizing and Ni-P coating was analyzed using an optical and scanning electron microscope (SEM) and X-ray diffraction (XRD) technique. Results showed that Ni-P coating and carburizing are effective in increasing wear resistance of low alloy steel. However, the Ni-P coating is more effective in increasing the E–C resistance. Also, the results showed that Ni-P coating, carburizing and untreated carbon steel behaved as ductile materials under erosion and E–C tests, and the maximum mass loss occurred at an impact angle of 45 deg. The synergism ratio was the lowest for the Ni-P coating, indicating that Ni-P coating improved an anti-E–C wear resistance.