## 1 Introduction  
Nickel-based superalloys are intended for the manufacture of components used in the nuclear energy production industry, the chemical and petrochemical industries, aircraft gas turbines, and other hydromechanical equipment. The service properties (mechanical, physical, and chemical) of these engineering materials can be improved through alloying, the kinetics of solidification processes, and thermal and thermochemical treatments [1, 2]. The increase in operating speed of equipment involving pressurized fluids makes them prone to cavitation erosion, leading to reduced performance and lifespan. Cavitationerosion is characterized by the formation and collapse of voids or bubbles filled either with vapor or with a combination of vapor and gases within a liquid [1]. The collapse of these bubbles generates shock waves and/or localized high-amplitude microjets, which can reach velocities between 300 and 500 m/s [1; 2; 3]. The growth and collapse time of cavitation bubbles is on the order of milliseconds, and the microcurrents formed during their impulse exert surface pressures ranging from 1000 to 4000 MPa, which exceed the yield strength of most materials [2; 4; 5]. The accumulation of this load due to repeated collapses causes plastic deformation, mechanical work hardening, the formation of microcracks, and material loss, leading to accelerated wear and even damage to components [4; 5; 6]. The degradation process of metallic materials through cavitation progresses by wear and is mainly based on two responsible mechanisms:  
* Degradation by fatigue;
* Degradation by exceeding the shear strength or the cleavage fracture stress. Considering these mechanisms, the following guidelines can be indicated to increase resistance to cavitation erosion:  
* Increasing the mechanical strength characteristics (Rm, Rp0.2, and HV);
* Achieving a homogeneous and as fine as possible distribution of structural obstacles: for example, local dislocation clustering leads to crack formation;
* Ensuring acceptable deformability of the material so that stress concentrations can be relieved through slip processes. Several laboratory and small-scale testing methods have been developed for evaluating cavitation resistance, namely:  
* The ASTM G32 Vibratory Cavitation Test (introduced in 1972);
* The TVA High Velocity Jet Cavitation Test. Both tests have been widely used to classify the cavitation erosion resistance of over 200 industrial alloys. The results have shown that the high-velocity jet cavitation test produces very intense wear and can erode industrial materials in approximately 10 times less time compared to the vibratory cavitation test [1; 2; 3; 4; 5]. However, there are differences in hydrodynamics and fracture mechanics between the two methods [5]: the hydrodynamics of high-velocity water jet cavitation is achieved through the acceleration and deceleration of the liquid flow using ultra-high-pressure pumps (thousands of bars), whereas the hydrodynamics of ultrasonic cavitation relies on high-frequency sound waves to induce bubble formation in a cloud attached to the cavitated surface. From the perspective of how the cavitated surface is stressed, the vibratory test produces a large number of repeated impacts (with high density and frequency), involving shock waves and microjets of various sizes and velocities at arbitrary points, mainly causing elastic-plastic deformation, fatigue, and fracture. In contrast, the high-velocity water jet test generates a much smaller number of repeated impacts, in well-defined surface areas, leading to mechanical work hardening (strain hardening) of the surface. Improving the erosion resistance of materials involves optimizing both their bulk and surface properties [1; 2; 6]. Numerous research studies have investigated the effect of thermal, mechanical, and thermochemical treatments, as well as various high-performance coating techniques applied to substrates to reduce or prevent cavitation erosion.