Greater Erosion Resistance Research Articles

Study on the slurry erosion wear of polycrystalline diamond compacts for application in fluidic oscillators

Fluidic oscillator made of tungsten carbide, the core component of the fluidic hammer, has a significantly reduced service life under the erosion wear of drilling fluids with solid particles. Polycrystalline diamond composite (PDC) has the potential to solve this issue due to its extremely high hardness and wear resistance benefits. However, few studies on the slurry erosion wear of PDC have been reported. In this paper, a modified slurry erosion experimental device based on submerged abrasive water jets was used to study the erosion resistance of four grades of PDCs with grain sizes of 2–3, 5, 10 and 25 μm respectively. The erosion surface of the damaged PDC was observed by scanning electron microscope (SEM) and the erosive mechanism of the PDC was analyzed. The experimental results showed that PDC had excellent slurry erosion resistance. The erosion rate of PDC was 1/192–1/43 of that of tungsten carbide when the jet velocity was 100 m/s. The erosion rates of PDC increased with the rise of jet velocity, impact angle and erodent particle size. In addition, the erosion performance of debris represented by quartz to PDC is greater than that of weighting agents represented by barite and hematite. Further research also showed that PDC with fine grain has greater erosion resistance than PDC with coarse grain, except PDC2 ~ 3. At a high impact angle, the erosive mechanism was forming the craters due to the crushing of diamond grains and the pits due to the overall pullout of diamond grains, while at a low impact angle, the erosive mechanism was ploughing and forming directional craters.

Reducing the hydraulic erosion of sand using microbial-induced carbonate precipitation

Hydraulic erosion is one of the main causes of failure within earth dams and embankments. Various methods are used to mitigate against such erosion, a common approach being grouting with cement, clay or chemical materials. Biogrouting using the microbial-induced carbonate precipitation technique is a relatively new, cost-effective, technically appropriate and environmentally friendly soil improvement method. Bacteria injected into the soil produce urease enzyme, which converts urea to ammonium and carbonate, causing calcite precipitation that binds soil grains together. In this study, the erodibility parameters of dense silica sand specimens treated with different injection strategies were investigated at bench scale. More effective treatment – in terms of greater and more uniform calcite precipitation over the test-specimen length, and hence greater erosion resistance – was achieved by aeration during solution injections and by incorporating a drained stage between injection cycles. With the latter, calcite precipitated as larger crystals, accumulating extensively over grain surfaces and also formed integrated in the pore voids. The best-performing treatment strategy produced a 95% reduction in erodibility and a five-fold increase in critical shear stress relative to untreated sand. These findings were confirmed by scanning electronic microscopy and calcium carbonate titration tests.

Calibrated CFD erosion modeling of abrasive slurry jet micro-machining of channels in ductile materials

Abrasive slurry jet micro-machining (ASJM) uses a relatively high-speed jet of fine abrasive slurry to precisely machine controlled-depth micro-features such as channels. Existing surface evolution models, developed for air-driven erosion processes, cannot account for the effect of slurry flow on the channel sidewall erosion that leads to the progressive channel widening observed in the ASJM of ductile materials. This paper presents a novel numerical–empirical model to predict the profiles of micro-channels in ductile materials (i.e. polymethylmethacrylate (PMMA), 6061-T6 aluminum alloy, 316L stainless steel and Ti–6Al–4V titanium alloy) using ASJM. The specific erosion rates of these materials were measured as a function of jet angle using a 10μm nominal diameter aluminum oxide slurry. The erosion rate-impact angle relations were corrected using computational fluid dynamic (CFD) models to account for the local impact angles and velocities of the particles. The erosion rate-impact angle relations were then used in three-dimensional CFD models to obtain the particle trajectories, impact angles, and velocities on a shallow eroded profile, and thus predict the erosion for deeper profiles. The model was verified by comparison with experiments which showed the previously-observed widening of the machined channels as the depth increased due to secondary erosion by particles impacting the channel sidewalls. The widening effect was found to be substantial in the PMMA but less important in Ti–6Al–4V titanium alloy due to its greater erosion resistance. The numerical–empirical approach could accurately estimate the widening and predicted the channel cross-sections up to an aspect ratio of approximately 1 with a maximum error of less than 5%.

Microstructural developments during erosion of tribological steels

Know-how of microstructural developments during erosion of 52100 and M50 tribological steels and associated erosion resistance knowledge are required for enhancement of properties. Erosion induced microstructural features such as disintegration of martensite boundaries, normal growth of martensite lath, low angle grain boundaries, shear bands, dislocation cell structure and independent recovery islets. Fraction of low angle grain boundary was larger after oblique erosion of 52100 steel while less shear bands were produced after oblique erosion compared to normal erosion. 52100 steel also developed independent recovery islets with tight packed dislocation wall and recovered cell interior. M50 ferrite developed dislocation cell structure during normal erosion. In general normal impact has been associated with greater erosion resistance. Comparatively less ploughing has increased erosion resistance of M50 ferrite than that of M50 martensite. Normal erosion resistance of 52100 and M50 martensite has been observed to be equal.

Erosion Study of New Orleans Levee Materials Subjected to Plunging Water

During Hurricane Katrina, overtopping water caused erosion and subsequent failure of several sections of I-type flood walls in New Orleans. Erosion stemmed from the kinetic energy of water falling from the top of the flood wall, unlike the typical surface erosion caused by shear flow. This study evaluated the effects of important parameters of levee soils—fines content, degree of compaction (DOC), clay mineralogy, and water content in relation to the erosion behavior of New Orleans levees subjected to the plunging water. In general, test results showed that a higher fines content contributed to greater erosion resistance. The trend became unclear when fines content exceeded 20–25%. A higher degree of compaction did not necessarily contribute to greater erosion resistance. Underwater soaked soils showed much less erosion resistance than nonsoaked soils. Soils containing expansive clay minerals showed less erosion resistance than soils containing nonexpansive clay minerals.

An experimental study on the erosion behavior of pseudoelastic TiNi alloy in dry sand and in aggressive media

The corrosive erosion behavior of Ti–51at.%Ni alloy under different erosion conditions was studied and compared to that of 304 stainless steel. Erosion tests were performed in a slurry-pot tester with dry sand, 3.5% NaCl slurry and 0.1 mol l −1 H 2SO 4 slurry containing 30% silica sand, respectively. Synergistic effects of corrosion and erosion were studied in steady corrosion, polarization, dry sand errosion and micro-wear experiments. An electrochemical-scratching test characterized the failure and recovery of the passive film formed on TiNi alloy in 3.5% NaCl and 0.1 mol l −1 H 2SO 4 solutions, respectively. In both dry sand and the corrosive media, the TiNi alloy exhibited considerably greater erosion resistance than 304 stainless steel.

The structure and properties of heat-treated and coated W-Mo-V+Si+Nb high-speed steels

Abstract This paper presents the results of investigations regarding the phase transformations occurring during the heat treatment of W-Mo-V + Si + Nb high-speed steels. It was found that investigated steels demonstrate their maximum secondary hardness, about 66 HRC, in connection with the precipitation of M 4 C 3 carbides in tempered martensite after austenitizing at 1240°C and tempering at 540–570°C. The paper presents also results of investigations regarding the erosion resistance of TiN and Ti(C,N) PVD coatings deposited on the investigated steels. TiN and Ti(C,N) coatings deposited in the PVD process yield, respectively, three and seven times greater erosion resistance of the steel surface and demonstrate good adhesion to the investigated steels forming the substrate. Quantitative metallography methods as well as mass loss and created craters 3-D measurements were employed to evaluate the erosion resistance of the investigated coatings. It was found that the surface topography influences the erosion resistance of PVD vacuum arc method coatings. The investigated coatings are not affected by the type of the substrate high-speed steels.

Microstructure and solid particle erosion of carbon-based materials used for the protection of highly porous carbon-carbon composite thermal insulation

Multiparticle erosion tests were performed on candidate coating (colloidal graphite paints) and cladding (dense carbon–carbon composites and graphite foil) materials employed to protect porous carbon–carbon composite thermal insulation in vacuum and inert-gas furnaces that utilize inert gas quenching. The dependence of the erosion rate on the angle of incidence of the erodent was examined and related to the microstructure and the mechanisms of material removal as observed by SEM. In addition, the effect of a thin chemical vapour deposited (CVD) carbon layer on top of a colloidal graphite paint coating and a graphite foil clad was investigated. The coating and cladding materials displayed a greater erosion resistance at all angles of incidence compared to the porous carbon–carbon composite. In general, the greatest erosion rate was found at an angle of incidence of 90°, where the erodent stream is perpendicular to the erosion surface, and brittle fracture was the predominant mechanism of material removal. The exception was the graphite foil material which displayed maximum erosion at an angle of incidence of 60°. For this material, two mechanisms were effective: disruption of the graphite flakes, which are mainly held together by mechanical locking, and a ploughing-like mechanism. The addition of a thin CVD carbon layer to colloidal graphite paint improved performance, whereas the erosion resistance of the graphite foil was slightly degraded as the CVD layer was too thin to prevent the ploughing-like mechanism.

Erosion-resistant materials for critical areas of coal liquefaction and coal gasification systems

Erosion has been encountered and has caused severe problems in a number of the prototype plants used to evaluate liquefaction and gasification processes. Analysis of the causes of these problems and of the available engineering systems solutions has shown that, in many cases, the rate of loss can be reduced to acceptable levels by careful attention to process control, component design, and materials selection. Nevertheless, some areas of recurring erosion problems are likely to remain, especially in the areas of raw material preparation and handling, and in effluent handling and disposal systems. Components such as valves and pumps are probably the most critically affected because of their importance to process control and safety, and because they are high cost items. Some areas of the associated piping, especially bends, and solids clean-up equipment such as cyclones and hydrocyclones may also be included in this category, but are more amenable to maintenance. Such critical areas can usually justify the application of the most erosion-resistant materials available, which are cermets or ceramics. These materials exhibit orders of magnitude better erosion resistance than the best metallic systems, but are also considerably more expensive and more difficult to apply. The WC-Co-base cermets have shown good performance as small inserts in valves in severe service in liquefaction plants. Laboratory studies in an erosion rig designed to simulate essential aspects of these service conditions have revealed relationships between erosion rates and materials properties such as hardness, fracture toughness, and microstructural parameters. It appears that a minimum erosion rate occurs at intermediate values of the materials properties, the reasons for which are discussed. Ceramic materials offer potentially greater erosion resistance and reduced costs, especially for larger sizes, compared to the WC-Co cermets. Rig test results confirm the potential for reduced erosion, but illustrate the profound effects of microstructure on the erosion behavior of a given ceramic. This has significant implications for both the manufacture of components and for techniques used to apply ceramics in, for instance, critical areas of valve and pump internals. Essentially, candidate ceramics exhibited one of two types of erosion behavior in the rig tests; ceramics within each group were found to show some relationship between hardness and erosion resistance. In practice, the application of ceramic materials will require revised handling and possibly operating procedures, and may require redesign of components to accommodate their low fracture toughness.

Erosion of conventional and ultrafine-grained materials

The erosion behavior was investigated of wear-resistant coatings of SiSiC and WWC applied to steel and graphite substrates using the controlled nucleation thermochemical deposition (CNTD) process, a refinement of the chemical vapor deposition (CVD) process. This process produces ultrafine equiaxed crystallites with average grain sizes of the order of tens to hundreds of ångströms. The room temperature erosion behavior of these materials was determined and compared with that of other conventional ceramic and metallic composite wear-resistant materials. The effects of various erodents, impingement angles and post-deposition heat treatments were investigated. The CNTD process produces materials with greater erosion resistance than that of conventional CVD materials and can be modified to deposit coatings onto ferrous alloys at low deposition temperatures. The erosion mechanism for CNTD materials is of the brittle type where the erosion rate is determined by the rate of initiation and propagation of cracks. It was found that post-deposition heat treatment of the CNTD WWC deposited at low temperatures improved the material's erosion resistance.