S. P. Kumaresh Babu

Sliding Wear Behavior of Graphite Filled Glass-Epoxy Composites at Elevated Temperatures

Effect of filler material on sliding wear behavior of Glass-Epoxy (G-E) composites has been investigated. The sliding distance, applied load, sliding velocity and temperature are the parameters used for the study. The fabricated wear specimens were tested by using pin-on-disk test rig. The result shows that the wear loss increases with increase in temperature and applied load and under the same conditions the coefficient of friction decreases. However, graphite-filled G-E composite exhibits lower wear rate and lower coefficient of friction as compared to unfilled composite. The features of worn surfaces of the specimens were examined under scanning electron microscope.

Erosive Wear Behavior of Nickel-Based High Alloy White Cast Iron Under Mining Conditions Using Orthogonal Array

Nihard Grade-4, a nickel-bearing cast iron widely used in slurry pumps and hydrodynamic components, is evaluated for its erosive wear response under mining conditions using a statistical approach. Experiments were conducted by varying the factors namely velocity, slurry concentration, angle of impingement, and pH in three levels, using L9 orthogonal array. Analysis of variance was used to rank the factors influencing erosive wear. The results indicate that velocity is the most influencing factor followed by the angle of impingement, slurry concentration, and pH. Interaction effects of velocity, slurry concentration, angle of impingement, and pH on erosion rate have been discussed. Wear morphology was also studied using SEM characterization technique. At lower angle (30°) of impingement, the erosion of material is by micro fracture and shallow ploughing with the plastic deformation of the ductile austenitic matrix. At the normal angle (90°) of impingement, the material loss from the surface is found because of deep indentation, forming protruded lips which are removed by means of repeated impact of the erodent.

Studies on Erosive Wear Behavior of UHMWPE-Filled Aramid–Epoxy Hybrid Composites

The effect of ultrahigh molecular weight polyethylene (UHMWPE) on mechanical and solid particle erosive wear behavior of aramid fabric reinforced-epoxy (A-E) composites has been investigated. The UHMWPE-filled aramid fabric reinforced-epoxy composites have been fabricated with varying particle concentration from 0 to 4 wt% by using a vacuum assisted resin transfer molding (VARTM) technique. The erosive wear rate was evaluated at different impingement angles from 30° to 90° and at three different velocities of viz., 20, 30, and 40 m/s, and at constant standoff distance. The silica sand of size 150–280 µm was used as erodent. The results reveal that erosive wear rate of UHMWPE in aramid-epoxy composite exhibits lowest value as compared to unfilled A-E composites, and maximum erosion rate was observed at an impingement angle 60°, and the material behaves in a semiductile manner. The morphologies of eroded surface were examined by the scanning electron microscope (SEM) in order to establish the erosion mechanism of the composites.

Erosive Wear Behavior of High-Alloy Cast Iron and Duplex Stainless Steel under Mining Conditions

Centrifugal pumps used in the lignite mines encounter erosive wear problems, leading to a disastrous failure of the pump casings. This paper attempts to evaluate the erosive wear resistance of Ni-Hard 4, high-chromium iron, and Cast CD4MCu duplex stainless steel (DSS), for mining conditions. The prepared test coupons were subjected to an erosion test by varying the impingement velocity and the angle of impingement, under two different pH conditions of 3 and 7, which pertained to the mining conditions. XRD analysis was carried out to confirm the phases present in the alloy. The eroded surface was subjected to SEM analysis to identify the erosion mechanisms. The surface degradation of Ni-Hard 4 and high-chromium iron came from a low-angle abrasion with a grooving and plowing mechanism at a low angle of impingement. At normal impingement, deep indentations resulted in lips and crater formations, leading to degradation of the surface in a brittle manner. A combined extrusion-forging mechanism is observed in the CD4MCu DSS surface at all the impingement angles.

Erosion Behaviour of WC–Co–Cr Thermal Spray Coated Grey Cast Iron under Mining Environment

Hydraulic machinery components made of grey cast iron (FG 260 grade) are preferred for engineering application because of their excellent damping properties. However when such materials are exposed to mining environments they exhibit poor erosion resistance without meeting their estimated life time. In order to enhance the service life of the material of hydraulic components, WC–Co–Cr thermal spray coating was identified. Grey cast iron samples (FG 260 grade) with and without WC–Co–Cr coating were subjected to slurry jet erosion tests by varying the impingent velocity and angle under two different pH levels at 3 and 7 which pertain to the mining environment. XRD characterization was done to identify and confirm the carbide phases present. Surface morphology studies were carried by SEM on both the substrate and coating, which revealed the erosion of grey cast iron surface, due to ploughing mechanism. In the case of WC–Co–Cr coating, at oblique angle of impact, the degradation is by micro cutting of the matrix and ploughing mechanism. At normal impingement, the fluctuating stress creates the cracks, which interlink each other and thereby causing erosion of the material.

Optimization of GMAW Process Parameters in Austenitic Stainless Steel Cladding Using Genetic Algorithm Based Computational Models

Weld cladding is a process of depositing a thick layer of anticorrosive metal on a corrosive substrate surface to impart better corrosion resistance properties. In weld cladding process, the difficulty generally encountered will be the problem of selecting optimum combination of input process parameters to achieve the desired dilution level. Until recently trial and error methods were employed to determine the optimum process parameters, which result in wastage of cost and time. This paper focuses on optimization of GMAW process parameters, which are used for deposition of austenitic stainless steel on low carbon structural steel plates. Experiments were conducted based on four-factor five-level central composite rotatable design with full replication technique. Mathematical models relating to gas metal arc welding process parameters to clad bead geometry were developed using multiple regression method. Developed mathematical models are helpful in predicting the clad bead geometry and in setting process parameters at optimum values to accomplish the desirable dilution level at relatively low cost with a high degree of reproducibility. The accuracy of the results was tested by conducting conformity tests using the same experimental set up. Moreover, Genetic Algorithm tool with GUI available in MATLAB 7.0 was used to optimize the process parameters to achieve optimum dilution.

Dispersion and Thermal Analysis of Carbon Nanotube Reinforced AA 4032 Alloy Produced by High Energy Ball Milling

In this work, multi-walled carbon nanotubes (MWNTs) were successfully reinforced in AA 4032 nanocrystalline matrix. The elemental powders of AA 4032 composites were mechanically alloyed in the high energy ball mill for 30 h to get nanocrystalline structure. The carbon nanotubes (CNTs) were added at the 29th hour of ball milling process. The morphological changes during milling were studied, using scanning electron microscope analysis and the distribution of the CNTs within the aluminum matrix was successfully revealed, using transmission electron microscope analysis. The results show that the CNTs are effectively distributed within the aluminum matrix without any structural damage. The variation in the melting point was studied using simultaneous thermal analyzer.

Three-Body Abrasive Wear Behavior of Basalt and Glass Fabric Reinforced Epoxy Composites

Three-body abrasive wear behavior of basalt–epoxy (B–E) and glass–epoxy (G–E) composites have been investigated using Dry sand rubber wheel abrasion resistance for various abrading distance, viz., 150, 300, 450 and 600m and different loads(22N and 32N) at 200 rpm. The weight loss and specific wear rate as a function of load and abrading distance were determined. The weight loss increases with increasing load and also with abrading distance while the specific wear rate decreases with increase in abrading distance and increases with the load. Better abrasion wear resistance was observed in B-E composite compared to G–E composite. Scanning Electron Microscope (SEM) is used to examine the abraded composite specimens and revealed that the more damage occur to glass fiber compared to basalt fiber. Also good interfacial adhesion was observed between epoxy and basalt fiber which leads to good abrasive wear resistance.

Solid Particle Erosion of UHMWPE Filled Aramid Fabric-Epoxy Hybrid Composites

The effect of ultrahigh molecular weight polyethylene (UHMWPE) on solid particle erosion behaviour of aramid fabric reinforced-epoxy (A-E) hybrid composites was investigated. The aramid fabric reinforced-epoxy hybrid composites have been fabricated with and with out UHMWPE filler. The solid particle erosive wear was evaluated at different impingement angles from 300 to 90 0 at constant velocity and at constant standoff distance .The silica sand of size 30 -50 and 60 -80 μm was used as erodent. The results show erosive rate of UHMWPE filled aramid- epoxy composite shows lowest value. The presence of UHMWPE in epoxy matrix gives good bonding between filler and matrix. The morphologies of eroded surface were examined by the SEM in order to establish the erosion mechanism of the composites.

Corrosion behavior of as-cast Mg–8Li–3Al+xCe alloy in 3.5wt% NaCl solution

Mg–8Li–3Al+xCe alloys (x = 0.5wt%, 1.0wt%, and 1.5wt%) were prepared through a casting route in an electric resistance furnace under a controlled atmosphere. The cast alloys were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The corrosion behavior of the as-cast Mg–8Li–3Al+xCe alloys were studied under salt spray tests in 3.5wt% NaCl solution at 35°C, in accordance with standard ASTM B–117, in conjunction with potentiodynamic polarization (PDP) tests. The results show that the addition of Ce to Mg–8Li–3Al (LA83) alloy results in the formation of Al2Ce intermetallic phase, refines both the α-Mg phase and the Mg17Al12 intermetallic phase, and then increases the microhardness of the alloys. The results of PDP and salt spray tests reveal that an increase in Ce content to 1.5wt% decreases the corrosion rate. The best corrosion resistance is observed for the LA83 alloy sample with 1.0wt% Ce.