Cavitation erosion is a critical problem for many engineering components, such as ship propellers, diesel engine exhaust valves, cylinder liners, pump impeller blades, hydraulic turbines, and bearings, which are exposed to high-velocity flowing fluids or to vibratory fluid motion. It represents a mechanical degradation of the surface caused by the continuous collapse of bubbles in the surrounding liquid, which seriously affects flow efficiency and component service life, increasing maintenance frequency and refurbishment costs. The intensity and evolution of the cavitation erosion phenomenon depend on the hydrodynamic conditions to which the component surface is exposed, the properties of the liquid, and the judicious selection of the most suitable material. This paper aims to modify the microstructure of a Ni-based superalloy by applying recrystallization annealing heat treatment in order to obtain surfaces resistant to cavitation erosion for components that handle fluids under local pressure fluctuations. Experimental tests are carried out using a vibratory apparatus with piezoceramic crystals operating at a frequency of 20 kHz and an amplitude of 50 µm. The cavitation erosion performance of the Ni-based superalloy INCONEL 625, heat treated by recrystallization annealing, are compared with that of austenitic stainless steel AISI 316L subjected to solution treatment. For both metallic alloys, based on mass loss measurements, the characteristic time-dependent curves of the mean cumulative erosion penetration depth, MDE(t), and the mean erosion rate, MDER(t), are determined. The comparison of these curves and of the parameters defined and recommended by the ASTM G32 standard demonstrates that, for the Inconel 625 superalloy, resistance to cavitation erosion increases by 77–81% compared to that of AISI 316L austenitic stainless steel. X-ray diffraction analyses (XRD) show that, in the microstructure of the Inconel 625 superalloy, in addition to austenite, MC-type carbides, M₂₃C₆ carbides, and intermetallic phases γ″ = Ni₃(Nb, Al, Ti) and δ = Ni₃(Nb, Mo) are also present.

The paper presents the results of the behavior and resistance to the erosion by cavitation of the 2017 A aluminium alloy structure, obtained by the WIG remelted method. The research is in step with the new directions of study and aims to extend the aluminum alloy 2017 A to the manufacture of parts that work in the cavitation regime, such as: pistons and valves of thermal engines, respectively various pump rotors or motor boat propellers. The analysis performed on the basis of the specific curves, constructed according to the indications of the ASTM G32-2016 normas, shows that structure, obtained by the WIG remelting, confers a constant behavior to the cyclic stresses of microjets generated by the hydrodynamics of the vibratory cavitation. The comparison of the results, based on the specific parameters, used in the laboratory and indicated by the ASTM G32-2016 norms shows a resistance to cavitation erosion, clearly superior to the semi-finished structure and those obtained by artificial aging heat treatment at 1800C and 120 0C, with duration of one hour.

Cavitation-induced degradation of metallic materials presents a significant challenge for engineers and users of equipment operating with high-velocity fluids. For any metallic material, the mechanical strength and ductility characteristics are controlled by the mobility of dislocations and their interaction with other defects in the crystal lattice (such as dissolved foreign atoms, grain boundaries, phase separation surfaces, etc.). The increase in mechanical properties, and consequently the resistance to cavitation erosion, is possible through the application of heat treatments and cold plastic deformation processes. These factors induce a series of hardening mechanisms that create structural barriers limiting the mobility of dislocations. Cavitation tests involve exposing a specimen to repeated short-duration erosion cycles, followed by mass loss measurements and surface morphology examinations using optical microscopy and scanning electron microscopy (SEM). The results obtained allow for a detailed study of the actual wear processes affecting the tested material and provide a solid foundation for understanding the degradation mechanism. The tested material is the Ni-based alloy INCONEL 625, subjected to stress-relief annealing heat treatment. Experiments were conducted using an ultrasonic vibratory device operating at a frequency of 20 kHz and an amplitude of 50 µm. Microstructural analyses showed that slip bands formed due to shock wave impacts serve as preferential sites for fatigue failure of the material. Material removal occurs along these slip bands, and microjets result in pits with sizes of several micrometers.

Aluminum alloy 6082 is known for its use in the manufacture of structures that require welding interventions, high mechanical properties, resistance to pressure and corrosion, such as: boilers, truck structures, bicycles and motor boats. The recent research, regarding the cavitation resistance of the this alloy structure, shows a poor behavior of the semi-finished structure and somewhat improved by artificial aging volumetric heat treatment regimes. On the line of increasing the resistance of the this alloy structure, to the erosive demands of cavitation, they sign up of the rechearch results of the this paper, regarding the behavior and resistance of the vibratory cavitation of the aluminum alloy 6082 structure , obtained by WIG remelting. Comparing with the results obtained on the structures in the semi-finished state and through volume thermal treatments of artificial aging state, using the established parameters, recommended by the ASTM G32-2016 norms, a significant increase in the resistance to cyclic cavitation stresses is found, as a result of the increase in the surface hardness value. The novelty of the work consists in motivating the use of the remelting procedure of the surface structure of aluminum alloy 6082, through WIG remelting in order to increase the surface hardness, with a direct effect on increasing this structure resistance to the cyclical fatigue stresses of shock waves and microjets developed through the hydrodynamic mechanism of cavitation.