Improving Cavitation Erosion Resistance Research Articles

Study on cavitation erosion resistance of bimodal grain copper alloy fabricated by laser shock peening

The surface of marine fluid operating machinery is commonly damaged by cavitation, and the protection of its surface is one of the key technologies in contemporary marine industry. Bimodal grain weaving is an important means to enhance the cavitation erosion (CE) resistance of materials. Traditional bimodal grain fabrication methods are based on the grain refinement-recrystallization principle or on the mixed powder sintering principle, which are too tedious. In this paper, laser shock peening (LSP), a convenient technique, is innovatively utilized to fabricate bimodal grain weaving on the surface of nickel-aluminum bronze (NAB), a material with excellent cavitation erosion resistance, by using the principle of inhomogeneity Gaussian beam laser shock peening. The mechanism of its cavitation erosion resistance is also investigated. The results show that the depth of the affected layer induced by laser shock peening can reach 460 μm. At a laser power density of 5.37∗107 J/cm2, a bimodal grain weave with a large number of micron-sized grains interwoven with ultrafine grains is formed on the NAB surface. The results of ultrasonic cavitation experiments show that the cavitation erosion resistance of bimodal grain surface fabricated by laser shock peening is improved by approximately 2.18 times than that of matrix. The synergy of strength and toughness of bimodal grains is one of the important reasons for the improved cavitation erosion resistance of NAB. This research is expected to further promote the application of bimodal grain weaving in the marine high-speed flow-passing components.

Mo-alloyed stainless steel coating with improved cavitation erosion resistance by plasma spraying a specially designed core-shell-structured powder

Plasma spray coatings are widely used to protect materials from cavitation erosion. However, the limited interlamellar bonding and porous structure of plasma spray coatings limit the potential of utilization of the coating materials for cavitation protection. In the present study, to improve the resistance of cavitation erosion for plasma spray coatings, molybdenum (Mo)-alloyed stainless steel coating with enhanced interlamellar bonding was deposited by spraying a specially designed core-shell-structured Mo-clad-304SS powder through shrouded plasma spray. The post-spray diffusion heat treatment was then also performed to further enhance the lamellar interface bonding of the coating. Owing to the high susceptibility to cohesion of the coating, cavitation erosion test was performed on the surface of resultant coatings to evaluate the quality of the interlamellar bonding within the coating. Results show that the cavitation erosion resistance of the 304SS-17Mo alloy coating with enhanced interlamellar bonding was significantly improved by 100% compared with that of conventional 304SS coating. After diffusion heat treatment, the cavitation erosion resistance of 304SS-17Mo alloy coating was further improved to as high as that of 304SS bulk due to the newly formed hard phases.

Cavitation erosion resistance enhancement of the surface modified 2024T351 Al alloy by ultrasonic shot peening

In this study, a novel surface strengthening method for improving cavitation erosion resistance by ultrasonic shot peening (USP) was proposed. Modified 2024T351 aluminium alloy surface layer with the characteristics of refined grains size, increased microhardness and residual compressive stress was prepared by USP treatment. Then the ultrasonic cavitation erosion (UCE) behaviour of the processed 2024T351 Al alloy was investigated. Results indicated that under the combined action of surface hardening and residual compressive stress, the cavitation weight loss of the USP-ed sample was significantly reduced. For the USP-ed 2024T351 Al alloy with an intensity of 0.101mmA, the weight loss after 3 hours' UCE treatment was reduced by 54.2 % compared to the untreated sample. This study also found that the increased surface roughness during shot peening could reduce the cavitation resistance properties. However, the weakening can be avoided by surface finishing. Results indicate that USP is a potential physical strengthening method that can significantly improve the cavitation erosion resistance of metals.

Effect of the reversal of the layer thickness ratio in the CrN/CrCN multilayer coating on cavitation-induced degradation

CrN/CrCN multilayer coatings with reversal ratios of layer thickness (1:2 and 2:1) and uncoated 1.4021 steel substrate were tested against cavitation erosion. Mechanical properties of the coatings were investigated. The CrN/CrCN coating with a layer thickness ratio of 2:1 (CrN_2–1 coating) had higher hardness, H, Young's modulus, E, and adhesion, i.e. LC2 force (the friction force in a scratch test at which the coating is completely removed) than the CrN/CrCN coating with a layer thickness ratio of 1:2 (CrN_1–2 coating). However, the CrN_2–1 coating had lower stiffness (the H/E and H3/E2 ratios) and LC1 force (the friction force at which the first coating failure occurs). Cavitation tests were carried out using a tunnel with a system of barricade exciters. Both coatings improved cavitation erosion resistance. The erosion rate of all tested materials started with the highest erosion rates which then decreased. After the cavitation tests, the erosion rate of 1.4021 steel was 50% higher than the erosion rate of the CrN 1–2 coating and 122% greater than the erosion rate of the CrN_2–1 coating. The H·LC2/E parameter better than the H/E ratio correlated with the volume loss of the tested coatings in cavitation erosion tests. Deep cracks and pits, and the dense network of cracks were the reason for the higher roughness of uncoated steel compared to coated steel. The maximum Ra roughness parameter of 1.4021 steel was from 60% to about 100% bigger than those obtained for coatings. Thicker layers of CrN in the multilayer CrN/CrCN coating led to a reduction in the density and size of pits due to a higher ability to absorb the impact energy compared to the coating with the thicker CrCN layers.

Development of Cavitation Erosion–Resistant Microwave Processed WC-based Cladding

In the present work, we investigated the effectiveness of microwave processing and thermal spraying for developing tungsten carbide (WC)-based erosion-resistant claddings. The microwave cladding showed a columnar structure with a well-bonded interface compared to discrete splat morphology and discontinuous interface of the thermal spray coating. The cladding showed a lower hardness (800 HV) compared to thermal spray coating (1,300 HV) and a two times higher fracture toughness due to the absence of splat boundaries and pores. The microwave cladding also showed 14 times and 10 times higher cavitation erosion resistance than thermal spray coating and SS316L substrate steel, respectively. The improved cavitation erosion resistance of the microwave cladding is explained on the basis of the optimized combination of hardness and fracture toughness. The surface of eroded cladding showed plastically deformed micropits compared to the thermal spray coatings, which showed large craters. Results show that microwave claddings can help improve the durability of engineering systems.

Correlation of Residual Stresses and Coating Properties in Arc-Sprayed Coatings on Different Substrates for Maritime Applications

Arc spraying is a cost-effective technology, which is determined by a few key factors. It is already established for corrosion protection of large structures and thus considered for restoration of eroded ship rudders and propellers by depositing typical propeller materials. The main parameters like arc current, gas type/flow or process kinematics strongly influence the residual stresses in these coatings, which in turn affect coating properties. In past investigations, it was shown that this impact could be modified by using alternative gas mixtures or changing the heat input in the process. However, the mentioned studies neglect the influence of the substrate, since solely steel substrates were used. In consequence, propeller alloys CuAl9Ni5Fe4Mn (Ni-Al bronze) and CuMn13Al8Fe3Ni2 (Mn-Al bronze) were now arc-sprayed onto bronze substrates while using the same parameters and kinematics as in the past. For reproducible results, the residual stresses within the coatings were measured by novel incremental hole drilling method based on electronic speckle pattern interferometry (ESPI) and correlated with the other coating properties. In comparison with spraying onto steel, the same conditions led to reduced Young’s moduli, lower tensile stresses and improved cavitation erosion resistance, while other properties like hardness and electrical conductivity showed varying trends.

Improvement in cavitation erosion resistance of AA5083 aluminium alloy by laser shock processing

Aluminium alloys are commonly used to manufacture the components that service under cavitation erosion environment. However, their poor cavitation erosion performance results in a significant reduction in their service life. In this study, a novel surface treatment method for improving cavitation erosion resistance by laser shock processing (i.e. laser shock peening with ablative coating (LSP) and laser shock peening without ablative coating (LSPwC)) was proposed. The microstructure, microhardness and residual stress of AA5083 aluminium alloy after laser shock processing were investigated. The cavitation erosion experiments were performed by ultrasonic cavitation. The cumulative mass loss, maximum surface damage depth, surface roughness and eroded surface morphologies during the cavitation erosion tests were characterized. The results indicate that laser shock processing can lengthen the incubation period and decrease the mass loss. The cavitation erosion resistance of LSP and LSPwC specimens is about 1.45 and 2.13 times that of substrate after 300 min cavitation erosion test, respectively. The eroded surface of substrate shows more serious damage morphology than that of treated specimens. The enhancement of cavitation erosion resistance for treated AA5083 aluminium alloy is ascribed to the refined grain and surface compressive residual stress, which can hinder the crack initiation and propagation, thereby inhibiting material spalling during cavitation erosion.

A Comparative Study of Cavitation Erosion Resistance of Several HVOF-Sprayed Coatings in Deionized Water and Artificial Seawater

In this study, WC-10Co4Cr coatings, Co-based coatings, WC-10Co4Cr/Co-based composite coatings, and Fe-based amorphous/nanocrystalline coatings were prepared on 316L stainless steel substrates by a high-velocity oxy-fuel spraying process. The cavitation erosion resistances of all the coatings, as well as the stainless steel substrates, were investigated in deionized water and artificial seawater. Results show that the effect of marine corrosion on cavitation erosion was most significant on the stainless steels, WC-10Co4Cr coatings, and Co-based coatings, but negligible on the WC-10Co4Cr/Co-based composite coatings and the Fe-based amorphous/nanocrystalline coatings. The WC-10Co4Cr coatings (0.17 mm3/h) show improved cavitation erosion resistance than those of WC-10Co4Cr/Co-based composite coatings (0.21 mm3/h), 316L stainless steel substrates (0.22 mm3/h), Co-based coatings (0.30 mm3/h), and Fe-based coatings (0.47 mm3/h) in marine environments.

Low temperature plasma nitriding of a Co30Cr19Fe alloy for improving cavitation erosion resistance

Cobalt alloys are used when improved cavitation-erosion (CE) resistance is needed. Low temperature plasma nitriding - (LTPN) is known to greatly enhance the CE resistance of austenitic and duplex stainless steels, due to formation of a very hard, super-saturated fcc - phase, known as expanded austenite or S-phase. In this work, Low Temperature Plasma Nitriding of a non-standard Co-Cr alloy was carried out to explore the formation of an expanded S-phase hard layer and to assess its effect on the CE resistance of the Co-Cr alloy. The Co-Cr samples, containing α-fcc and ε-hcp solid solutions phases, were plasma nitrided at 350 °C and 400 °C for 20 h. The CE tests were carried out in a vibratory cavitation equipment according to ASTM G32-92. Microstructural and micromechanical characterization of the specimens indicated the formation of an expanded S-phase fcc layer, containing small amounts of CrN. Plasma nitriding at 400 °C and greater amounts of α-fcc volume fraction in the matrix led to thicker and harder (10.5 GPa) S-phase layers. The 400 °C nitrided samples exhibited higher CE resistances than the non-nitrided samples, with up to 267% greater incubation times and 5 times reduced wear rate. All Co30Cr19Fe samples showed higher CE resistances than AISI 304 and only the solution-treated sample showed lower CE resistance than Stellite 6. The results are discussed in terms of the mechanisms of material removal, during the initial stages of CE, which are controlled by plastic deformation, with formation of slip steps, grain boundaries protrusion and material removal from these protruded areas. Twin boundaries are preferably eroded. The increase in nitrogen content increases the elastic energy returned to the environment and decreases the amount of plastic energy absorbed by the alloy, at cavitation impact spots.

Friction stir processing of dual certified 304/304L austenitic stainless steel for improved cavitation erosion resistance

Cavitation erosion is known to be prevalent in equipment in hydraulic environments. Understanding cavitation erosion and improving the erosion resistance of commonly used materials is of interest for both scientific and economic reasons. In this study, friction stir processing was employed to modify commercial dual certified AISI 304/304L austenitic stainless steel plates. The cavitation erosion behavior of the processed plates was evaluated and compared to that of the unprocessed steel. A temperature control algorithm was employed to maintain a target tool temperature during the processing. The cross sections of the processed nuggets were evaluated using optical microscopy, scanning electron microscopy and Vickers hardness testing. Erosion testing by cavitation liquid jet was performed conforming to ASTM G134 on specimens cut out of the nuggets of the commercially unprocessed and the processed 304/304L steel. The tool temperature was found to affect the microstructure and the cavitation erosion behavior. Friction stir processed steel showed greater than 3× improvement in cavitation erosion resistance (defined as the reciprocal of the mass loss of a given material) than the unprocessed 304/304L. Surface erosion patterns and erosion rates were characterized and the mechanisms of material removal were discussed.

The synergistic effect of cavitation erosion and corrosion of nickel-aluminum copper surface layer on nickel-aluminum bronze alloy

A completely nickel-aluminum-copper (Ni-Al-Cu) layer was obtained through thermal diffusion process on a nickel-aluminum-bronze (NAB) substrate. The cumulative mass loss of the NAB alloy during the cavitation erosion tests was about 6.4 times and 5.5 times as large as that of the Ni-Al-Cu layer in distilled water and 3.5 wt% sodium chloride (NaCl), respectively. Electrochemical measurements under quiescence and cavitation erosion conditions were conducted to investigate the synergistic effects of cavitation erosion and corrosion. The results showed that the synergism had measurable effect on the cavitation erosion-corrosion process for both the NAB alloy and the Ni-Al-Cu layer. The total contribution of the cavitation erosion component including WE and WCIE was more than 80% and WE occupied the largest percentage. Thus, the improved cavitation erosion resistance of the Ni-Al-Cu layer was mainly due to mechanical factors, which implied a homogeneous and refined microstructure and the formation of hardened Ni3Al phase.

Improving cavitation erosion resistance of austenitic stainless steel in liquid sodium by hardfacing – comparison of Ni and Co based deposits

Cavitation affects the performance of hydraulic machinery and also results in erosion damage. Although the damage produced in sodium is more intense than that in water, it is uneconomical to design hydraulics to totally avoid cavitation. The designer is left with the choices of improving hydraulic design and/or using materials/coatings with good resistance to cavitation. Susceptibility to cavitation is evaluated for two different hardfaced coatings, viz. Co-based Stellite6® alloy coatings and Ni-based Colmonoy5® coatings, and the results compared with that for 316L austenitic stainless steel. Study reveals that Stellite6 alloy coating is more resistant to cavitation than Colmonoy5 in liquid sodium. However, the cavitation resistance of Colmonoy5 coating is better than that of austenitic stainless steel 316L, the substrate material on which these alloys are deposited. Results are explained based on the differences in the stacking fault energy and fracture toughness of the materials.

Cavitation erosion resistance of two steels with the same percentage of Chromium and Nickel but different Carbon content

Hydraulic machinery repair works necessitate new materials with improved cavitation erosion resistance and simultaneously good welding properties. The present paper is concerned with the behavior at cavitation of two steels with close contents of chromium (approximately 12%) and nickel (approximate 6%) but with different carbon content (for the first 0.1% C and the second 0.036% C). The reduced carbon content is necessary for an easy welding repair work. As a result of the different chemical content, as is shown by the Schäffler diagram, the steel containing 0.1% C has a structure formed by 60% austenite and 40% martensite while those with 0.036% C has completely martensitic structure. The laboratory tests were done in two vibratory devices one with piezoelectric crystals, respecting the ASME G32-2010 Standard and the other a magnetostrictive vibratory device with nickel tube. The evaluation of the cavitation resistance was obtained with the help of cavitation erosion characteristic curves MDE (t) and MDER (t). For analyzing the steel degradation, the eroded areas were also subjected to microscopic investigations. The results show that the steel with 0.1% C has better cavitation erosion behavior than that of the steel with 0.036% C.

Surface modification by gas nitriding for improving cavitation erosion resistance of CP-Ti

Gas nitriding process has been used to increase the surface hardness of titanium, in this study we used this technique to improve the cavitation erosion resistance (Rce) of commercial purity titanium (CP-Ti). We also studied microstructure, phase constituents, hardness and the effect of processing parameters on Rce of the treated samples. The results indicated that the Rce of the treated samples was related to the processing parameters. The sample treated at 850°C for 4h has the highest Rce, which was attributed to the compound layer (CL) with a hard, dense and free-defects microstructure. With increasing the nitriding temperature and duration, the Rce of the treated samples decreased due to the excessive oxide and defects formed in the CL. When the CL was removed, the treated sample exhibited an excellent cavitation erosion behavior. It was supposed to be due to the existence of the residual compressive stresses field in the nitrogen diffusion zone, which played an important role in preventing microcracks initiation and propagation to interior for cavitation damage.

Cavitation erosion resistance of NiTi thin films produced by Filtered Arc Deposition

In this study, NiTi thin films were obtained by using a Filtered Arc Deposition System (FADS). X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were used to investigate the effect of substrate temperature (130–600 °C) on the structures and properties of NiTi thin films. It was found that FADS produced dense and homogenous films. Higher substrate temperatures resulted in crystalline thin films dominated by the parent phase (B2). The cavitation erosion resistance of the films was assessed by using ASTM Test Method G32. It was found that NiTi thin films showed superior cavitation erosion resistance compared with 316 austenitic stainless steel. The improved cavitation erosion resistance was attributed to the recoverable deformation associated with pseudoelasticity of the NiTi thin film.

Effect of boron addition on the cavitation erosion resistance of Fe-based hardfacing alloy

The cavitation erosion behavior of Fe–Cr–C–Si– xB ( x = 0, 0.3 and 0.6 wt.%) alloys were investigated up to 50 h by using 20 kHz vibratory cavitation erosion test equipment. The boron-added alloys showed the improved cavitation erosion resistance compared to the boron-free alloy. This improvement was attributed to that the boron addition enhanced the grain boundary strength and refined the grain size of the matrix. However, the cavitation erosion rate of the 0.6 wt.% boron specimen was higher than that of the 0.3 wt.% boron specimen. The higher erosion rate of the 0.6 wt.% boron was due to the larger carbide volume in the matrix.

Hydrogen effect on the cavitation erosion resistance of AISI 316L stainless steel laser surface-modified with NiTi

AISI 316L stainless steel was laser surface-modified with NiTi for improving cavitation erosion resistance as reported in a previous study. The present study aimed at investigating the effect of hydrogen charging on the cavitation erosion resistance of the NiTi-modified layer, in comparison with 316L substrate and bulk NiTi plate. To compare the hydrogen effect, the three types of samples were subjected to the same electrolytic charging intensity. The change in surface morphology and in the phases present was studied by scanning-electron microscopy and X-ray diffractometry. The indentation properties were studied using Vickers microhardness test and nanoindentation test. Cavitation erosion test indicated that hydrogenation resulted in different degrees of decrease in erosion resistance in all the three types of samples, which could be attributed to different mechanisms. For 316L, the hydrogen effect was mild, congruent with the small change in indentation properties. For NiTi-modified 316L, the decrease in resistance was due to a drop in hardness and elasticity, while for bulk NiTi, the decrease was mainly attributable to the formation of hydrides leading to the presence of surface cracks.

Study on the cavitation erosion behavior of hardfacing alloys for nuclear power industry

The cavitation erosion behavior of wear resistant hardfacing alloys for nuclear power industry Co-base Stellite 6 and new Fe-base alloy was investigated using 20 kHz vibratory cavitation erosion test equipment. Although the crack was initiated at the carbide-matrix interfaces, the matrix hardened by strain-induced phase transformation from austenite to martensite effectively repressed the crack propagation. The cumulative weight loss of new Fe-base alloy was about 2.40 mg/cm 2 after exposing to cavitation for 150 h and the cavitation erosion characteristic was similar to that of Stellite 6 on the whole range. The improved cavitation erosion resistance of new Fe-base alloy was due to the matrix hardening by the strain-induced phase transformation and to the small volume fraction of the carbide-matrix interface acting as crack initiation sites.

Laser surfacing of S31603 stainless steel with engineering ceramics for cavitation erosion resistance

As a preliminary study on incorporating ceramic particles into stainless steels for improving cavitation erosion resistance, ceramic-reinforced coatings were fabricated on austenitic stainless steel UNS S31603 using a laser surfacing technique. Ceramic powders, including WC, Cr 3C 2, SiC, TiC, CrB 2 and Cr 2O 3, were used to produce surface metal matrix composites (MMCs) with high volume fractions of reinforcement. The powders were pasted on the surface of UNS S31603 first, followed by surface melting using a high power laser. The microstructures and structures of the surfaces were analyzed. The cavitation erosion characteristics of the surface-modified specimens in 3.5% NaC1 solution at 23°C were studied by means of a 20-kHz ultrasonic vibrator at a peak-to-peak amplitude of 30 μm. The cavitation erosion resistance R e of all the laser-modified specimens was improved, except for the case of Cr 2O 3, with the improvement depending on the microstructure formed. The R e of surface MMCs reinforced with CrB 2, WC and TiC increased to 9.4, 8.5 and 1.7 times that of monolithic S31603, respectively. For the specimens modified with Cr 3C 2 and SiC, a eutectic mixture of austenite and carbides or silicide was formed and the R e was increased by a factor of 4.8 and 2, respectively.