Slurry Erosion Characteristics Research Articles

SUPPORT VECTOR MACHINE LEARNING ON SLURRY EROSION CHARACTERISTICS ANALYSIS OF Ni- AND Co-ALLOY COATINGS

In this paper, a novel support vector machine (SVM) learning approach has been used to predict the silt erosion of coatings sprayed by the high-velocity oxy-fuel (HVOF) process. The silt erosion resistance of HVOF-coated Co- and Ni-alloys is studied using an erosion tester. Both of these spraying powders were deposited on the 18Cr-12Ni-2Mo austenitic steel substrate. For the erosion experiments, the fixtures were developed to test the erosion characteristics at different impingement conditions (i.e. [Formula: see text], [Formula: see text], and [Formula: see text]). The image processing technique enables an understanding of the erosion mechanisms of coatings. The support vector regression is more effective than the traditional regression models. The proposed model employs support vector regression with parameter tuning. The ideal parameters are selected with the help of the grid search method. The model is trained by supplying 70% data and validated with 15% data. Afterward, the remaining 15% is given to the prepared model as testing data. The dataset obtained is employed for building an effective support vector regression model. The predicted results are compared against the original experimental values. The developed model is also compared with other state-of-the-art machine learning techniques for showing the preciseness of the proposed model. The Ni-based HVOF coating showed superior performance ([Formula: see text]) better than the Co-based HVOF coating under similar experimental conditions. An SVM model was successfully developed to predict the erosion of coated and uncoated 18Cr-12Ni-2Mo austenitic steel. The precision performance of the SVM model was calculated in terms of [Formula: see text], RMSE, [Formula: see text], and MAE as 0.99, [Formula: see text], 0.99, and [Formula: see text], respectively.

Understanding the slurry erosion behaviour of iron-based chromium carbide coating material during deposition via arc spray coating method

The material S235JR was spray-coated with iron-based chromium carbide in the present study. The effects of the initial surface roughness on slurry erosion were investigated. Samples with a rough surface and polished surface were used. The impact of particle concentration, impact velocity and impact angle was studied on the slurry erosion characteristics in terms of mass loss, surface roughness and surface temperature. In addition, the surfaces were analysed using a scanning electron microscope (SEM). Further, the estimation equation has been derived using response surface method (RSM) based on the data obtained in the study. The results show that velocity and concentration are the key factors in determining the mass loss and surface temperature while the impact angle has a relatively minor role. Mass losses in rough samples ranged from 8.8 mg to 40 mg; in polished samples, the range ranged from 5.6 mg to 10.9 mg.

Influence of post clad heat treatment on microstructure and slurry erosion characteristics of Ni-based microwave clad

In this study, effect of high temperature heat treatment on microstructure and erosive wear performance of Ni-based clad was investigated. The clad was developed on a hydroturbine steel (CA6NM) substrate using microwave hybrid technique. The as-clad microstructure comprised of rod-like Cr enriched M7C3 carbides in γ-(Ni, Fe) solid solution. Post clad heat treatment at 750 °C led to M7C3→M23C6 transformation accompanied by increase in carbide volume fraction. On the other hand, heat treatment at 1000 °C clad resulted in partial dissolution of the eutectic carbides. Among the tested samples, 750 °C heat treated sample exhibited higher erosion resistance. The erosive wear behaviour of Ni-based clad, before and after heat treatment, showed good correlation with hardness (at 30°) and elastoplasticity (at 90°).

Effect of microwave exposure time on microstructure and slurry erosion behavior of Ni + 20% Cr7C3 composite clads

The phenomenon of slurry erosion in hydro turbines and its components is a major challenge. Microwave cladding is a potential surface modification technique to mitigate the effects of slurry erosion. Microwave exposure time during cladding could play an important role on the microstructure and performance of the developed clads. In the present work, Ni + 20 wt% Cr7C3 composite clads were developed on CA6NM hydro turbine steel using microwave cladding technique. The effect of microwave exposure time on clad microstructure and its subsequent effect on slurry erosion characteristics were studied. The developed clads were assessed in terms of their microstructure, phase analysis, nanohardness and fracture toughness using various techniques. Slurry erosion characteristics of the developed clad were studied using a slurry jet erosion test rig. The slurry erosion trials were performed at a jet velocity of 40 m/s with an impact angle of 90° for 120 min. Cumulative weight loss, wear rate and wear mechanisms were assessed to determine the slurry erosion performance of the developed clads.

Slurry erosion performance study of HVFS sprayed Ni-20Al2O3 and Ni-15Al2O3-5TiO2 coatings under hydro accelerated conditions

PurposeThis paper aims to cover all the aspects of development, investigation and analysis phases to evaluate the slurry erosion performance of test coatings. The powders having composition of Ni-20Al2O3 and Ni-15Al2O3-5TiO2 were deposited on CA6NM grade turbine steel by using high velocity flame spray (HVFS) technique. The characterization of the coatings was done with the help of SEM/EDS and XRD techniques. Various properties such as micro-hardness and bonding strength of the coatings were also evaluated. Thereafter, these coatings were subjected to an indigenously developed high speed slurry erosion tester at different levels of rotational speed, erodent particle size and slurry concentration. The effect of these parameters on the erosion behavior of coatings was also evaluated. The slurry erosion tests and SEM of the eroded surfaces revealed remarkable improvement in slurry erosion resistance of Ni-15Al2O3-5TiO2 coating in comparison with Ni-20Al2O3 coating.Design/methodology/approachTwo different compositions of HVFS coating were developed onto CA6NM steel. Subsequently, these coatings were evaluated by means of mechanical and microstructural characterization. Further, slurry erosion testing was done to analyze the erosive wear behavior of developed coatings.FindingsThe coatings were successfully developed by HVFS process. Cross-sectional microscopic analysis of sprayed coatings revealed a continuous and defect-free contact between substrate and coating. Ni-15Al2O3-5TiO2 coating showed higher value of bond strength in comparison with Ni-20Al2O3 coating. Under all the testing conditions, Ni-15Al2O3-5TiO2 coatings showed higher resistance to slurry erosion in comparison with Ni-20Al2O3 coatings. Rotational speed, average particle size of erodent and slurry concentration were found to have proportional effect on specific mass loss of coatings. The mixed behavior (brittle as well as ductile) of the material removal mechanism was observed for the coatings.Originality/valueFrom the literature review, it was found that researchers have documented the various studies on Ni-Al2O3, Ni-TiO2 and Al2O3-TiO2 coatings. No one has ascertained the synergetic effect of Alumina and Titania on the slurry erosion performance of Nickel-based coating. In view of this, the authors have developed Ni-Al2O3 and Ni-Al2O3-TiO2 coatings, and an attempt has been made to compare their mechanical, microstructural and slurry erosion characteristics.

Experimental investigation of slurry erosion characteristics of laser treated nickel aluminum bronze

Slurry erosion characteristics of laser surface processed commercial grade nickel aluminium bronze (NAB), treated with a pulsed Nd-YAG laser are discussed here. Laser surface processing of the test material, in the main, revealed the presence of β phase, contributing to its enhanced hardness. Slurry erosion tests, carried out as per Taguchi’s DOE protocol indicate that optimal laser parameters minimising the slurry erosion are laser power 100W, laser beam diameter 0.4mm and pulsing frequency of 10Hz. rapid cooling of the melt region has resulted in hard Widmantatten structure responsible for the improvement in slurry wear erosion. Examination of the SEM images of the laser treated surface exposed to 15 Hours of slurry erosion reveal minimal micro cutting, micro ploughing and corrosion pits in comparison to the untreated surface under identical levels of erosion.

Slurry erosion characteristics and erosion mechanisms of stainless steel

In the present study, slurry erosion experiments of stainless steel SUS-304 were carried out using new advanced erosion test rig, where the multiphase flows of alumina sand and water were utilized as the erodents. The results show that erosion rate was initially high and gradually reduced over the testing time. In addition, the erosion rate increased with an increase in impact velocity. The surface roughness increased with either increasing testing time or impact velocity. Further, the surface profiles of “W” shape were observed for all eroded samples. Microstructural characterization reveals two different erosion regimes: plastic deformation mechanism dominated at high impact angles, while plowing/cutting mechanism dominated at low impact angles. A correlation between the erosion rate, erosion profile and microstructure is also discussed.

A fuzzy model for evaluation and prediction of slurry erosion of 5127 steels

This paper introduces a fuzzy logic model to evaluate and predict the slurry erosion of ductile materials in engineering and chemical applications. There are seven variables which have the most significant influences on the slurry erosion of ductile material, and must be taken into considerations. These are impact angle, time, roundness factor, aspect ratio, particle size, impact velocity and concentration of the particles. By using the fuzzy rules which can be generated based on some experimental observations, a two-layer fuzzy model could be developed to correlate these variables to the slurry erosion (weight loss of material). The model is based on the assumption that the slurry erosion characteristics of ductile materials is an imprecise complex function of many interacting variables, and can be described and evaluated by the theory of fuzzy sets. Membership functions and fuzzy rule-base for application to slurry erosion of 5127 steel as a ductile material are presented in detail to demonstrate the effectiveness of fuzzy logic in modeling such a complex system in an efficient way. This constructed model would facilitate the development of an expert, real-time and integrated system using fuzzy logic technology to monitor the level of the slurry erosion process.

Slurry Erosion Characteristics and Erosive Wear Mechanisms of Co-Based and Ni-Based Coatings Formed by Laser Surface Alloying

In the present work, an attempt has been made to study the slurry erosion properties and operating erosive wear mechanisms of Co-based Stellite 6 and Ni-based Colmonoy 88 coatings, and also to list the conditions at which maximum and minimum erosion rates occur. Laser surface alloying (LSA) has been done on 13Cr-4Ni steels with commercial Co-based Stellite 6 and Ni-based Colmonoy 88 powders. Slurry erosion tests have been conducted on LSA-modified steels for a constant slurry velocity of 12 m/s and for a fixed slurry concentration of 10 kg/m3 of irregular, sharp-edged SiO2 particles with average sizes of 375 and 100 μm and at impingement angles of 30, 45, 60, and 90 deg. A mixed (neither ductile nor brittle) mode of erosion behavior for Stellite 6 coatings and a brittle mode of erosion behavior for Colmonoy 88 coatings were observed when these materials were impacted with particles with an average size of 375 μm, whereas only a brittle mode of erosion was observed for both Stellite 6 and Colmonoy 88 coatings when impacted with particles with an average size of 100 μm. Mainly, chip formation, chip fracture, microcutting, plowing, and crater lip and platelet formation were observed for Stellite 6 coatings and progressive fracture of carbides, carbide pullout and carbide/boride intact were observed for the case of Colmonoy 88 coatings.

A FUZZY MODEL FOR EVALUATION, PREDICTION AND CONTROL OF SLURRY EROSION OF DUCTILE MATERIALS

This paper introduces a fuzzy logic model to evaluate, predict and control the slurry erosion of ductile materials in engineering and chemical applications. There are seven variables which have the most significant influences on the slurry erosion of ductile material, and must be taken into considerations. These are impact angle, time, roundness factor, aspect ratio, particle size, impact velocity and concentration of the particles. By using the fuzzy rules which can be generated based on some experimental observations, a two-layer fuzzy model could be developed to correlate these variables to the slurry erosion (weight loss of material). The model is based on the assumption that the slurry erosion characteristics of ductile materials is an imprecise complex function of many interacting variables, and can be described and evaluated by the theory of fuzzy sets. Membership functions and fuzzy rule-base for application to slurry erosion of 5127 steel as a ductile material are presented in detail to demonstrate the effectiveness of fuzzy logic in modeling such a complex system in an efficient way. This constructed model would facilitate the development of an expert, real-time and integrated system using fuzzy logic technology to monitor and control the level of the slurry erosion process

Erosion wear behavior of laser clad surfaces of low carbon austenitic steel

Austenitic steel surfaces are laser cladded using a 4 kW continuous wave CO 2 laser with coaxial powder feeding nozzle to investigate the improvement in slurry erosion characteristics. Colmonoy-6 and Inconel-625 are cladded on AISI 316L steel and AISI 304L steel, respectively by laser cladding. Initially, single-pass clad track is overlaid to optimize the laser processing parameters, namely scanning speed and powder feed rate to obtained a sound clad. Minimum cracks, porosity and distortion were found at scanning speed of 0.1 m/min and powder feed rate of 12 g/min. For these parameters, the dilution was 17.33% for Colmonoy-6 and 40% for Inconel-625. To clad large surface area, the optimized laser processing parameters were used to deposit the clad tracks with 60% overlap. Maximum surface hardness of 746 VHN is obtained in case of Colmonoy-6 clad on AISI 316L steel and is 352 VHN in case of Inconel-625 clad on AISI 304L steel. EDAX analysis shows higher degree of mixing of substrate material in the clad pool of Inconel-625 than Colmonoy-6. The results of slurry erosion test of Colmonoy-6 clad surface have shown improvement in erosion resistance of the order of 1.75–4.5 times of the substrate AISI 316L steel at all impact angles and the maximum wear angle has also increased which can be attributed to the increase in the surface hardness. However, Inconel-625 laser clad surface has shown little improvement in erosion resistance of the substrate AISI 304L steel at shallow impact angles with no significant improvement at normal impact condition. The SEM micrographs of worn out Colmonoy-6 clad surfaces at shallow impact angles show that the material is removed mainly by micro-cutting which increases with increase in the impact angle.

Effect of increased manganese addition and mould type on the slurry erosion characteristics of Cr-Mn iron systems

The wear resistance of high chromium iron is well recorded. However, the same is not the case as regards the use of manganese at higher percentages in high chromium irons and its influence on wear behaviour. Hence, this work highlights the slurry wear characteristics of chromium (□ 16–19%) iron following the introduction of manganese at two levels i.e. 5 and 10%. It is known that the wear properties are dictated by the microstructural features. To alter the structure, the cooling rate of casting has been varied by adopting two different types of moulds (i.e. sand and metal) and subsequently subjecting to thermal treatment. The as-cast and heat treated samples are examined for microstructure and then evaluated for hardness and slurry erosion properties. As the manganese content is increased from 5 to 10%, the hardness showed a decrease in value both in the as-cast and heat treated conditions. The slurry erosion loss, expectedly, showed an increase irrespective of the sample condition (i.e. mould type/heat treatment adopted). The findings are corroborated with the microstructural features obtained through optical and scanning electron microscopy.

A study of high-speed slurry erosion of NiCrBSi thermal-sprayed coating

The test specimens of NiCrBSi coating were prepared using the high velocity oxy-fuel spraying technique with a post-thermal treatment. Their high-speed slurry erosion characteristics have been systematically studied. SUS304 stainless steel was selected as the comparison material. Experimental results show that the NiCrBSi sprayed coating exhibits a much better slurry erosion resistance than the SUS304 stainless steel. The erosion rate for the NiCrBSi sprayed coating slightly increases with the impinged angle. However, a maximum erosion rate appears at an impinged angle of around 30° for SUS304 stainless steel. Both NiCrBSi sprayed coating and SUS304 stainless steel exhibit impinged surfaces with lots of furrows at an impinged angle of 30°. At a high impinged angle of 90°, the SUS304 stainless steel exhibits an impinged surface with lots of overlapping and irregular concavities, while, these features are less obvious for NiCrBSi sprayed coating. The hardness of SUS304 stainless steel increases significantly with increasing impinged angle during the high-speed slurry erosion. But, there is no obvious work hardening for the NiCrBSi sprayed coating due to its extra-high hardness and less plastic deformation, even at a high impinged angle of 90°.

A comparison of slurry erosion characteristics of TiNi shape memory alloys and SUS304 stainless steel

The slurry erosion characteristics of three TiNi shape memory alloys and SUS304 stainless steel using the liquid/solid impingement have been systematically studied. Experimental results show that more resistant TiNi alloys and less resistant SUS304 stainless steel exhibit ductile behavior and the maximum erosion has observed at 30°. The surface morphologies exhibit many long furrows and ridges at low impingement angles. The exponent in the relation ε= kV n varied between 2 and 3 for impingement angles between 15° and 90°. Work hardening of surface is observed on the surface of all tested materials. The work hardening layer and thin platelet formation increase with angle of impingement. The SIM formation and pseudoelastic behavior of TiNi B2 phase, and variant accommodation and SIP formation of TiNi martensite, make important contributions to the slurry erosion resistance of TiNi alloys.

Slurry erosion characteristics of TiN coatings on α-Ti and plasma-nitrided Ti alloy substrates

The slurry erosion behavior of TiN coatings on α-Ti and plasma-nitrided Ti alloy substrates in aqueous silica slurry has been investigated using a jet-in-slit rig. Erosion tests were performed with slurry jet velocities between 6.4 and 15.2 m s−1. At the lower slurry velocity, pitting was caused by the slurry impact, and there was little volume loss for each of the coatings. The TiN coatings deposited on the α-Ti and nitrided Ti alloy substrate presented high slurry erosion resistance. With increasing slurry velocity, however, perforation and fragmentation of the hard TiN coatings occurred and the protection effect of the coating layer reduced with the erosion duration. The erosion rates for the coatings deposited on the nitrided Ti substrate were slightly lower than those for the coatings deposited on the α-Ti substrate under the same test conditions. After coating perforation, the surfaces of the substrates were eroded by crater formation and flaking on the center section of the erosion scars while cutting and plowing occurred at the outer regions of the erosion scars.

Slurry erosion resistance of Al18B4O33 whisker-reinforced AC4C Al alloy matrix composites

Abstract Slurry erosion resistance of as-cast and T6-treated 19.5 vol.% Al 18 B 4 O 33 whisker reinforced AC4C Al composites and AC4C Al alloys was investigated at room temperature. Erosion tests were performed with slurry having jet velocity range 6.4–15.2 ms −1 and at normal impact angle, and a sand concentration of 20 wt%. Scanning electron and optical microscopy were used to characterize the microstructure of the materials and the mechanisms of the slurry erosion. The results indicated that the slurry erosion characteristics of the materials were affected by the particle velocity and material properties. At low slurry velocities, the erosion resistance for the MMCs was improved as a result of whisker addition. However, steady-state rate was found to increase with the addition of whisker to the matrix alloy at high slurry velocities. Age-hardening (T6) treatment was not effective in improving the erosion resistance of the composites. High erosion rate in the whisker reinforced MMCs can be attributed to reduced fracture strain. In addition to plastic deformation, for the composites, surface fracture and dislodgement of Al 18 B 4 O 33 whisker occurred under high-velocity slurry impact conditions. By considering the material removal processes, a simple rationalization of the inverse dependence of slurry erosion rate on He f was obtained.

減圧プラズマ溶射したセラミックコーティング材料のスラリーエロージョン特性

減圧プラズマ溶射したセラミックコーティング材料のスラリーエロージョン特性

High silt wear of hydroturbine runners

Turbine runners show an unusually high rate of wear in river water with a high silt content. Cast ferritic stainless steel of CA6NM type is the normal turbine runner material. The slurry erosion characteristics of stellite 6, 15wt.% Cr-15wt.% Mn stainless steel, type 316L stainless steel and CA6NM were evaluated in a specially designed equipment. The different wear rates of the alloys are explained in terms of the microstructure, hardness and work-hardening rate.