الفهرس 
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Abstract
Cavitation, a repeated formation and violent collapse of bubbles in a liquid created by pressure changes, can result in deformation and erosion of material in the vicinity of the bubbles. Cavitation erosion is one of the main types of damage on hydraulic machinery, such as propellers, pumps, piping systems and large turbines. Some components are often exploited under complex conditions simultaneous of cavitation, corrosion and erosion wear and it would lead the components to fail early and cause huge economic loss. As the cavitation erosion occurs at the liquid/ solid interface, thus it is related to surface properties rather than bulk properties, the cavitation erosion resistance of a component may be improves by some surface engineering techniques. Surface enguineering techniques have the advantage of consuming only a small amount of expensive material on the surface while using an inexpensive substrate for the bulk. Therefore, the research on surface engineering techniques and coating materials are emphasized for enhancing the cavitation erosion resistance of mechanic parts in the recent years. However, the problem of protecting hydraulic machine surfaces still remains in many cases unresolved, because the erosion of different iron-base metals is much differentiated and the material resistance to cavitation action also depends on intensity of the loading and type of the impingement. In the present work, the cavitation erosion-corrosion performance od structural steel (AISI 1045), electroless coated by Nickel-Phpsphorus was investigated. The study taking into consideration the effect of plating solution properties such as pH, agitation effect, chemical composition of the coating solution, as well as the effect of heat treatment at different temperatures.
The cavitatioin environment was provided by an ultrasonic cavitation apparatus using an ultrasonic induced cavitation facility with modified method. Two different corrosive mediums, tap water and 3% NaCl solution were used to study the effect of bath type, heat treatment temperature and plating solutions composition on the cavitation erosion-corrosion process. For comparing the effectiveness of electroless plating, the results of substrate material (1045 steel) under similar condition were presented. The microstructure of electroless plating under different controlling parameters was identified using XRD. Then the morphology of damafe surfaces and wear debris were investigated ising optical and scanning electron microscopy. The cavitation erosion-corrosion resistance was measured using the gravitational method.