Higher Cavitation Erosion Resistance Research Articles

Effect of residual stress and phase constituents on corrosion-cavitation erosion behavior of 304 stainless steel by iso-material manufacturing of laser surface melting

Different from additive manufacturing and subtractive manufacturing, iso-material manufacturing (also named isovolumetric manufacturing) is applied to 304 stainless steel (304SS) by laser surface melting (LSM) at four energy density (51 J/mm2, 44 J/mm2, 39 J/mm2, 37 J/mm2), aiming at improving the resistance to corrosion and cavitation erosion without any addition of precious metals. The experimental results show that the microstructure presents the transformation from plane crystal → columnar crystal → equiaxed crystal from interface to top surface. All the samples exhibit austenite+martensite+Cr23C6, and the martensite content is increased from 9.3% to 40.8% with the energy density decreasing after iso-material manufacturing. In addition, low angle grain boundary is increased, and nano-mechanical properties also show an increasing trend. The decreasing of energy density also enhances the residual tensile stress of the melting layer. The sample obtained at energy density of 51 J/mm2 displays the highest corrosion resistance in 3.5 wt% NaCl solution, which can be attributed to its low galvanic corrosion degree and small residual tensile stress. The sample obtained at energy density of 39 J/mm2 exhibits the highest cavitation erosion resistance (Re) and its passivation film displays better self-repairing and re-passivation ability as indicated by synergistic cavitation erosion-corrosion behavior. The high cavitation erosion resistance can be attributed to the proper compromise of the constituent phases and higher self-repairing of the passivation film for the melting layer. Moreover, the 304 stainless steel prepared in this study exhibits a high or comparable corrosion and cavitation erosion resistance in comparison with the samples prepared by other fabrication method reported previously.

Comparison of the cavitation erosion and slurry erosion behavior of cobalt-based and nickel-based coatings

Cobalt-based and nickel-based coatings were successfully produced using TIG welding and laser cladding technologies as alternative materials with higher cavitation erosion (CE) and slurry erosion (SE) resistance, respectively. Their structure, phase constitution, hardness and elastoplasticity were characterized. Combined with the cumulative mass loss, erosion morphology and roughness, the CE and SE resistances were compared and erosion models were also proposed. The results show that the cobalt-based coating exhibited much better CE resistance and lower SE resistance than the nickel-based coating. The phase transition contributes mostly to the high CE resistance of the cobalt-based coating. While, the combined effects of high hardness, elastoplasticity and hard phases' anchoring and shielding, determine the high SE resistance of the nickel-based coating.

Effect of solution treatment on cavitation erosion behavior of high-nitrogen austenitic stainless steel

The effect of solution treatment on the cavitation erosion behavior of a Fe-18Cr-16Mn-2Mo-0.66 N high-nitrogen austenitic stainless steel (HNSS) exposed in distilled water up to 8 h was investigated using magnetostrictive cavitation, micro-hardness, mass loss measurements, scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the solution treatment slightly decreased the hardness of the HNSS but significantly increased its elasticity. The HNSS with an improved elastic property was shown to have a higher resistance to the absorption of energy produced by cavitation erosion, and hence a higher cavitation erosion resistance. The cavitation erosion damage of the HNSS in distilled water was found to be a deformation-controlled process which limited by the formation and development of plastic deformation during cavitation erosion tests.

Microwave synthesized composite claddings with enhanced cavitation erosion resistance

In the current work we developed Ni-SiC based composite claddings on SS316L through microwave irradiation using different reinforcement weight fractions and particle sizes (micron to nano scale). A bimodal derivative using equal proportions of both micro and nano scale particles was also developed. Microstructural characterization showed claddings were composed of columnar structure with precipitated intermetallic phases segregated at the grain boundaries. The Ni-SiC bimodal particle reinforced claddings showed highest hardness and fracture toughness. All the developed claddings showed significantly high cavitation erosion resistance compared to SS316L steel. The Ni-10 wt% SiC bimodal particle reinforcement cladding showed highest erosion resistance with around 5 times lower erosion rates than SS316L steel along with highest incubation period. The investigated bimodal particle reinforced cladding also outperformed the thermal sprayed WC10Co4Cr and Stellite 6 coatings and CA6NM hydroturbine steel used for comparison. Detailed structure-property correlation analysis showed that the exquisite performance of the investigated bimodal particle reinforcement cladding can be ascertained to high hardness and H/E ratio (inversely related with plasticity index). Compared to brittle failure mode exhibited by thermal spray coatings due to splat delamination, the Ni-SiC claddings showed mixed signatures of both ductile and brittle failure modes. Examination of the eroded surfaces of the claddings showed presence of significant number of micro pits surrounded by extruded lips and dislodged intracellular phase. Detailed SEM analysis of the samples near incubation period showed damage accumulation initiated around these intermetallic phases in the form of cracks and pits. It was shown that Ni-SiC based microwave-derived bimodal particle reinforced claddings are an effective and efficient solution for countering the cavitation induced erosion in fluid machinery.

Corrosion and wear properties of FeCrMnCoSi HVOF coatings

FeCrMnCoSi coating (so-called CaviTec alloy) is recognized as an efficient protective measure to extend the service-life of steel components subjected to severe cavitation erosion. Besides this requirement, many applications also demand coatings with proper corrosion and wear resistances. The aim of this study is to evaluate the pitting corrosion and the sliding wear resistances of CaviTec coatings produced by high-velocity oxygen fuel (HVOF) and deposited onto a 304 stainless steel (SS). The corrosion performances in simulated seawater indicated that these coatings exhibit satisfactory corrosion resistance with regions around the inter-splats representing the preferential weak links sites for pitting corrosion initiation. CaviTec coating wear is characterized by mild delamination followed by severe abrasive wear once the hard-martensitic debris are added in the tribosystem due to the transformation induced plasticity (TRIP) effect. Corrosion and wear results point out that the CaviTec coatings, originally developed to possess high cavitation erosion resistance, also present satisfactory corrosion resistance in seawater-like medium and interesting dry sliding wear performance, which can extend their application domain.

On Surface Topography and Microstructure in Cavitation Erosion Tests of Alloy 80 A

From practical and economic reasons for the design of components for Diesel engines, the selection of materials and/or heat treatments is essential to provide a high cavitation erosion resistance. This paper studies cavitation behavior of the Nimonic 80A alloy designed for execution of Diesel engine exhaust valves. The cavitation tests where done on an ASTM G32 -2010 compliant vibrating device with piezoceramic crystals.The metalographic examinations performed with optical microscope and electronic scanning microscopy revealed the microstructural changes occurring in the region of the cavitation affected material and the path of the crack propagation

Cavitation Erosion Resistance and Wear Mechanism Model of Flame-Sprayed Al2O3-40%TiO2/NiMoAl Cermet Coatings

This manuscript deals with the cavitation erosion resistance of flame-sprayed Al2O3-40%TiO2/NiMoAl cermet coatings (low-velocity oxy-fuel (LVOF)), a new functional application of cermet coatings. The aim of the study was to investigate the cavitation erosion mechanism and determine the effect of feedstock powder ratio (Al2O3-TiO2/NiMoAl) of LVOF-sprayed cermet coatings on their cavitation erosion resistance. As-sprayed coatings were investigated for roughness, porosity, hardness, and Young’s modulus. Microstructural characteristics of the cross section and the surface of as-sprayed coatings were examined by light optical microscopy (LOM), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) methods. Coating cavitation tests were conducted in accordance with the ASTM G32 standard using an alternative stationary specimen testing method with usage of reference samples made from steel, copper, and aluminum alloys. Cavitation erosion resistance was measured by weight and volume loss, and normalised cavitation erosion resistance was calculated. Surface eroded due to cavitation was examined in successive time intervals by LOM and SEM-EDS. On the basis of coating properties and cavitation investigations, a phenomenological model of the cavitation erosion of Al2O3-40%TiO2/NiMoAl cermet coatings was elaborated. General relationships between their properties, microstructure, and cavitation wear resistance were established. The Al2O3-40%TiO2/NiMoAl composite coating containing 80% ceramic powder has a higher cavitation erosion resistance than the reference aluminium alloy.

Exceptionally high cavitation erosion and corrosion resistance of a high entropy alloy

Cavitation erosion and corrosion of structural materials are serious concerns for marine and offshore industries. Durability and performance of marine components are severely impaired due to degradation from erosion and corrosion. Utilization of advanced structural materials can play a vital role in limiting such degradation. High entropy alloys (HEAs) are a relatively new class of advanced structural materials with exceptional properties. In the present work, we report on the cavitation erosion behavior of Al0.1CoCrFeNi HEA in two different media: distilled water with and without 3.5wt% NaCl. For comparison, conventionally used stainless steel SS316L was also evaluated in identical test conditions. Despite lower hardness and yield strength, the HEA showed significantly longer incubation period and lower erosion-corrosion rate (nearly 1/4th) compared to SS316L steel. Enhanced erosion resistance of HEA was attributed to its high work-hardening behavior and stable passivation film on the surface. The Al0.1CoCrFeNi HEA showed lower corrosion current density, high pitting resistance and protection potential compared to SS316L steel. Further, HEA showed no evidence of intergranular corrosion likely due to the absence of secondary precipitates. Although, the degradation mechanisms (formation of pits and fatigue cracks) were similar for both the materials, the damage severity was found to be much higher for SS316L steel compared to HEA.

Cavitation erosion resistance of Ni-Co based coatings

The Ni-Co based coatings were performed by means of PTA method from Ni-based and Co-based powders. The cavitation erosion resistance of Ni-Co specimens and reference sample in deionized water was determined by the ultrasonic vibration system. The microstructure, as well as mechanism of cavitation erosion of coating was examined by using SEM and LOM. The main mechanism of erosion is cracking and spalling at the boundary of dendrites and eutectics. Coatings exhibit higher cavitation erosion resistance than the reference sample. Therefore, they could be applied to repair and protect pump elements from cavitation wear.

Experimental comparison of cavitation erosion rates of different steels used in hydraulic turbines

The prediction of cavitation erosion rates has an important role in order to evaluate the exact life of components in fluid machineries. Hydro-Québec has studied this phenomenon for several years, in particular in hydraulic turbine runners, to try to understand the different degradation mechanisms related to this phenomenon. This paper presents part of this work. In this study, we carried out experimental erosion tests to compare different steels used in actual hydraulic turbine runners (carbon steels, austenitic and martensitic stainless steels) to high strength steels in terms of cavitation erosion resistance. The results for these different classes of steels are presented. The tests have been performed in a cavitating liquid jet apparatus according to the ASTM G134-95 standard to simulate the flow conditions. The mass loss has been followed during the exposure time. The maximum depth of erosion, the mean depth of erosion, and the mean depth erosion rate are determined. As a result we found that ASTM-A514 high strength steels present excellent cavitation erosion resistance properties. The cavitation eroded surface is followed by optical profilometry technique. Determination of mechanical properties and examinations of the eroded surfaces of the samples have also been carried out in order to identify the erosion mechanisms involved in the degradation of these kinds of materials.

Cavitation erosion resistance of high nitrogen stainless steel in comparison with low N content CrMnN stainless steel

The cavitation erosion (CE) of a high nitrogen stainless steel (HNS) and a low nitrogen CrMnN stainless steel in both distilled water and 3%NaCl solution at 20±1°C was investigated by using a magnetostrictive induced cavitation facility. The evolution of CE with test time was analysed by morphology observation by SEM and roughness measurement after different CE intervals. The possible phase transformation of austenite to martensite due to cavitation was analysed by XRD, and cross-sectional microhardness after cavitation was also measured to evaluate the work hardening ability. The role of corrosion was analysed by polarisation curve. The test results indicated that HNS had a relatively higher CE resistance than CrMnN steel, which was mainly attributed to its higher work hardening ability, thicker wok hardening layer and lower stacking fault energy. Different from that of the HNS, many tiny cracks could be clearly seen in the cross-section of eroded CrMnN steel especially at the ferrite zones. The pure erosion dominated the whole cavitation damage process, and the synergistic effect between corrosion and erosion was relatively small for both steels. The CE behaviour of HNS was relatively more sensitive to the corrosion media than that of CrMnN steel. Therefore, it should be a little bit careful when HNS was used in corrosive media.

Cavitation erosion resistance of Fe-26Mn-6Si-7Cr-1Cu shape memory alloy

The cavitation erosion of low stacking fault energy Fe-26Mn-6Si-7Cr-1Cu shape memory alloy has been investigated in water using an ultrasonic vibratory apparatus, and compared with the behaviour of 0Cr13Ni5Mo stainless steel. It is shown that Fe-26Mn-6Si-7Cr-1Cu alloy has higher cavitation erosion resistance than 0Cr13Ni5Mo stainless steel. The cavitation erosion mechanism of Fe-26Mn-6Si-7Cr-1Cu was studied by examining the eroded surface using X-ray diffraction (XRD) and scanning electron microscopy (SEM). During early stages of cavitation erosion, Fe-26Mn-6Si-7Cr-1Cu alloy undergoes strain induced martensitic transformation. Exposure to further cavitation results in the deformation of ϵ martensite. The boundaries of ϵ martensite impede plastic deformation, leading to strain accumulation and subsequent material removal. On the basis of an XRD study and indentation tests, the better cavitaton erosion resistance of Fe-26Mn-6Si-7Cr-1Cu alloy is mainly ascribed to strain induced martensitic transformation, which can absorb impact energy without damage.

Effects of laser treatments on cavitation erosion and corrosion of AISI 440C martensitic stainless steel

Laser surface treatments with high and low fluence were employed to induce melting and transformation hardening on 440C. While melting could bring about better improvement in corrosion resistance, transformation hardening was more effective in enhancing the cavitation erosion resistance. Compared with conventional heat treatment, laser treatments resulted in higher corrosion resistance with a wide passive range in NaCl solution, and also in higher cavitation erosion resistance in both deionized water and NaCl solution.

Cavitation erosion behavior of Cr–Mn–N stainless steels in comparison with 0Cr13Ni5Mo stainless steel

The cavitation erosion (CE) behavior of two kinds of Cr–Mn–N stainless steels was investigated by means of an ultrasonic vibration processor and compared with that of 0Cr13Ni5Mo stainless steel, commonly used material for hydraulic turbines in China. The eroded surfaces after different CE duration were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Roughness ( R a) of the eroded surfaces was calculated from the measured profiles after different CE duration, and microhardness of cross-sections of the tested materials was also measured to indicate work-hardening ability. The results show that the CE resistance of austenitic single phase or austenite–ferrite duplex phase Cr–Mn–N steels is higher than that of the 0Cr13Ni5Mo martensitic stainless steel, which is mainly attributed to their high work-hardening ability. Different from 0Cr13Ni5Mo stainless steel, the cracks initiating in the eroded austenite of Cr–Mn–N stainless steels propagate nearly parallelly rather than normally to the surface, which is also beneficial to the resistance to CE. Low ferrite content is also found to be beneficial to improving the resistance to CE of duplex phase Cr–Mn–N stainless steels. It is supposed that in the case of Cr–Mn–N stainless steels the cavitation impingement energy could be absorbed and transferred into the inside of materials by the “forming and transferring” mode of the high hardness layer. Developing steel with high work-hardening ability and low ferrite volume content is possibly an important method to design steel with high CE resistance.

Cavitation erosion resistance of heat-treated NiTi

NiTi (Ti–50.8 at.% Ni) specimens were solution-treated at 1000 °C, followed by aging between 200 and 600 °C. The cavitation erosion resistance of all the aged specimens in deionized water was improved relative to the solution-treated specimen, with a maximum increase of about 8.7 times, which was achieved by aging at 500 °C. The results also indicate that both austenite and martensite contribute to the high cavitation erosion resistance of NiTi. It is also shown that a simple macro-indentation test employing a Rockwell indenter may be used for preliminary screening of heat-treated NiTi with respect to cavitation erosion resistance.

Cavitation erosion of duplex and super duplex stainless steels

Owing to their excellent corrosion resistance, stainless steels are widely used both in the marine, urban water, chemical and food industries. In addition to the corrosive environment, high fluid flow speeds are always encountered for components used in these industries. The cavitation characteristics of S30400 and S31600 austenitic stainless steels and duplex stainless steels were studied in detail by a number of authors. It was generally agreed that S30400 has higher cavitation erosion resistance than that of S31600 due to higher tendency of strain induced martensitic transformation under high impulse of stress. A considerable number of results on stress corrosion cracking characteristics of SDSS and duplex stainless steels have been published but data concerning their cavitation erosion property are extremely rare.

Wear resistance of titanium-alloyed high-aluminum bronzes under cavitation

Aluminum-nickel bronzes are known to have a high cavitation-erosion resistance; this is especially true of bronzes containing 11–14% Al, which can be used to restore worn parts of hydraulic engines, marine engines, etc. Analysis of the few publications shows that additional alloying with titanium is a promising way of optimizing the chemical composition of Al-Ni bronzes in order to enhance their cavitation wear resistance and cut costs. Sufficiently detailed information about the cavitation-erosion resistance and the nature of the fracture of microvolumes, however, is not available at present. This article deals with this.

Cavitation erosion of metals and alloys

Several high purity metals (aluminium, cobalt, chromium, copper, iron, magnesium, molybdenum, nickel, tungsten and zinc) and some commercial copper-, iron-, nickel- and cobalt-base alloys were investigated by weight loss measurements and by surface analysis with scanning electron microscopy and X-ray photoelectron spectroscopy. The results lead to the conclusion that the cavitation erosion resistance (CER) is decisively determined by the binding energy and the crystal structure of the base metal. The ability of alloys made of base metals with a high CER to deform and to transform allotropically is the second important factor.

Cavitation Erosion Resistances of Cast Iron and Chromium Films Plated on Cast Iron under Various Conditions

It is well known that pitting has often occurred on the water side of water cooled diesel cylinder liners. There has been but scanty record of studies made of the interrelations of cavitation erosion, the microstructure of cast iron, the hardness of chromium films plated on cast iron and the hardness of base metals studied.The present study was made with the aim to prevent pitting and to make clear the mechanism of cavitation erosion of cast iron and such chromium films. The magnetostrictive cavitation tests were carried out on specimens that are chromium films with various hardness plated on cast iron, various heat treated cast iron, chromium films with same hardness plated on various heat treated cast iron, carbon steel and chromium films plated on carbon steel.The results obtained are as follows(1) The high cavitation erosion resistance was obtained with plated chromium films of hardness between 850 and 900 Vickers hardness on specimens of chromium films with various hardness plated on cast iron.(2) The cavitation erosion resistance of cast iron increased with increasing hardness of cast iron. It seems that at first the cavitation erosion in the portion with graphite structure was caused by impact stress when cavities collapse, secondly the cracks grew up between graphite and graphite, and finally the destruction occurred.(3) The cavitation erosion resistance increased with increasing hardness of cast iron for specimens of chromium film with 874 Vickers hardness plated on various heat treated cast iron.(4) The high cavitation erosion resistance was obtained on specimens of chromium film plating on carbon steel.