B. B. Jha

Effect of Microstructural Variation on Erosion Wear Behavior of Ti-6Al-4V Alloy

The present article describes the effect of microstructural variations—that is, lamellar, bimodal, and equiaxed—on solid particle erosion wear behavior of Ti-6AL-4V alloy at room temperature. Erosion tests were carried out at various test conditions using an air jet–type test rig and Taguchis orthogonal array experimental design. The results indicated that impact velocity is the most significant controlling factor influencing the solid particle erosion wear of Ti-6Al-4V alloy followed by impact angle, microstructural variation, and size of erodent. The lamellar microstructure of Ti-6Al-4V alloy has excellent erosion resistance, followed by bimodal and equiaxed microstructures. Ploughing or pile-up leading to platelet formation was found to be the primary mechanism of material loss in erosion of Ti-6Al-4V alloy. This mechanism of material loss is independent of its microstructural variation. These results were determined after observation of the eroded surface under a scanning electron microscope. Optical microscopy, Rockwell hardness testing, and scanning electron microscopy were used to characterize the microstructures and eroded surfaces of the Ti-6Al-4V alloy in order to correlate the results obtained.

Erosive Wear Analysis of Plasma-Sprayed Cu Slag–Al Composite Coatings

This article depicts the solid particle erosion response of plasma-sprayed composite coatings using an industrial waste product (i.e., copper slag) and aluminum. The influence of five operating parameters—that is, impact velocity, erodent size, erodent temperature, impingement angle, and aluminum content of feedstock with four different levels each—on performance output (i.e., erosion rate) are studied using Taguchis L16 orthogonal array design. Out of the five parameters, impact velocity has been found to be most influential factor on the erosion wear rate of coated samples. Maximum erosion takes place at an impingement angle of 60°, showing the semiductile response of the coating to solid particle erosion. In addition, a multilinear mathematical equation is proposed in order to predict the wear rate. The percentage of error between experimental data and predicted data was small, with a very high correlation coefficient (r2) of 0.997 showing the correctness of the mathematical equation used.

Effect of primary alpha phase variation on mechanical behaviour of Ti–6Al–4V alloy

Abstract Small punch tests (SPTs) have been carried out at room temperature to correlate the microstructural variation of Ti–6Al–4V alloy with that of SPT parameters. Microstructural variation in terms of different volume fractions of primary alpha phase of Ti–6Al–4V alloy has been introduced as a result of solution annealing at different temperatures followed by thermal aging. Small punch test parameters, i.e. total area under the load vs displacement curve, area under the zone of elastic bending, plastic bending and plastic instability have been found to increase from the content of 10% primary alpha phase to 20% primary alpha phase and then these are decreasing from the content of 20% primary alpha phase to 30% primary alpha phase.

Deposition of plasma sprayed copper slag coatings on metal substrates

Abstract Copper slag is a waste product obtained during matte smelting and refining of copper. The present work explores the coating potential of copper slag by plasma spraying. This work shows that copper slag is eminently coatable. When premixed with alumina powder, the coating exhibits higher interfacial adhesion as compared to pure copper slag coatings. Maximum adhesion strengths of about 23 and 27 MPa are recorded in for the coatings of copper slag with 15 wt.% of alumina on aluminium and mild steel substrates respectively. The input power to the plasma torch is found to affect the coating deposition efficiency and morphology of the coatings.

Effect of Microstructural Degradation on Solid Particle Erosion Behavior of 2.25Cr-1Mo Steel

The present article evaluates the influence of independent control factors such as microstructural degradation, impact velocity, impingement angle, and erodent size on solid particle erosion behavior of 2.25Cr-1Mo steel using a statistical approach. Microstructural degradation in this steel has been introduced as a result of thermal aging corresponding to Larson-Miller parameter (LMP) values of 33,012, 35,402, 37,846, and 38,374. Solid particle erosion tests were carried out using a sand blast–type test rig following a well-planned experimental schedule based on Taguchis orthogonal arrays. The erosion rate of this steel decreases with increase in the severity of thermal aging. This observed phenomenon could possibly be attributed to spheroidization of lenticular-shaped carbides to globular-shaped carbides as a result of increase in the severity of thermal aging. With the help of signal-to-noise ratios and analysis of variance (ANOVA), an optimal combination of control factors to minimize the solid particle erosion behavior of 2.25Cr-1Mo steel was determined. Among all four control factors, the LMP representing the extent of thermal aging is the most significant control factor influencing the solid particle erosion behavior of this steel, followed by impingement angle, impact velocity, and size of erodent. Results indicated that the LMP has a greater static influence of 46.33%, impingement angle has an influence of 42.51%, impact velocity has an influence of 7.47%, and size of erodent has an influence of 1.13% on solid particle erosion of this steel. Material loss during solid particle erosion of 2.25Cr-1Mo steel is found to be ductile in nature and primarily controlled by cutting and ploughing action.

Experimental Study on the Effect of Microstructure on Dry Sliding Wear Behavior of Titanium Alloy Using Taguchi Experimental Design

The present article depicts the influence of independent control factors such as microstructural variation, normal load, sliding velocity, and test duration on the dry sliding wear behavior of titanium alloy at room temperature using a statistical approach. Different heat treatments were carried out in a controlled manner to produce various microstructural features (i.e., lamellar, bimodal, and equiaxed) in this alloy. A lamellar microstructure is found to be harder than bimodal microstructure followed by an equiaxed microstructure in this alloy. Dry sliding wear tests were carried out using a multiple tribotester following a well-planned experimental schedule based on Taguchis orthogonal arrays. The dry sliding wear behavior of this alloy consisting of various microstructural features is related to their hardness values. The results indicated that a lamellar microstructure has the lowest sliding wear resistance followed by bimodal and equiaxed microstructures. Using signal-to-noise ratios and analysis of variance (ANOVA), an optimal combination of control factors that minimize the dry sliding wear in this alloy were determined. Among all four control factors, normal load is the most significant control factor influencing the dry sliding wear behavior of the investigated titanium alloy, followed by microstructural variation, sliding velocity, and test duration. Normal load has a greater static influence of 39.53%, microstructural variation has an influence of 31.55%, sliding velocity has an influence of 21.6%, and test duration has an influence of 5.7% on the dry sliding wear of this alloy. Two wear mechanisms were identified: oxidative wear occurs at the lowest sliding velocity and delamination wear occurs at the highest sliding velocity. Optical microscopy, scanning electron microscopy, and Rockwell hardness measurements were used to characterize the microstructures in order to correlate the results obtained.

Influence of in-flight particle state diagnostics on properties of plasma sprayed YSZ-CeO2 nanocomposite coatings

This article describes the influence of controlling in-flight hot particle characteristics on properties of plasma sprayed nanostructured yttria stabilized zirconia (YSZ) coatings. This article depicts dependence of adhesion strength of as-sprayed nanostructured YSZ coatings on particle temperature, velocity and size of the splat prior to impact on the metallic substrate. Particle temperature measurement is based on two-color pyrometry and particle velocities are measured from the length of the particle traces during known exposure times. The microstructure and adhesion strength of as-sprayed nano-YSZ coatings were studied. Field emission scanning electron microscopy results revealed that morphology of coating exhibits bimodal microstructure consisting of nano-zones reinforced in the matrix of fully melted particles. The coating adhesion strength is noticed to be greatly affected by the melting state of agglomerates. Maximum adhesion strength of 42.39 MPa has been experimentally found out by selecting optimum levels of particle temperature and velocity. The enhanced bond strength of nano-YSZ coating may be attributed to higher interfacial toughness due to cracks being interrupted by adherent nano-zones.

Effect of Microstructure upon the Wear Properties of 2.25Cr-1Mo Steel

The present paper investigates the effect of microstructural variations upon the wear properties of 2.25Cr-1Mo steel using a dry sliding wear test. Optical, Scanning and Transmission Electron Microscopy (TEM) together with Energy Dispersive X-ray analysis (EDX) have been used to characterize the microstructures and identify the evolution of various precipitates in terms of their shapes, sizes and morphologies. The wear behavior of this steel was investigated using a disc-on-roller multiple wear tester under dry sliding conditions, rubbing against EN-31 steel. Samples were tested at 100N load and 500rpm sliding speed at room temperature. A decrease in wear loss was measured continuously for up to one hour for all the samples. The results indicated that the wear behavior of this steel was highly influenced by microstructural variations taking place during service exposure. The precipitation of globular Cr- and Mo-rich carbides has been found to improve the wear behavior of this steel at room temperature. Scanning Electron Micrographs (SEM) of worn surfaces have been used to correlate the results obtained

Influence of reinforcement and processing on steel-based composites: Microstructure and mechanical response

ABSTRACT Steel matrix composite reinforced with 2–4 vol.% titanium diboride particles was fabricated successfully by powder metallurgy route through hot pressing method. Influence of sintering parameters on densification was investigated by measurement of density of resultant composites. Microstructural analysis of hot-pressed materials was performed. Hardness and deformation behavior under constant load were evaluated by conducting microhardness and nanoindentation tests. The addition of titanium diboride proved to be effective for enhancement of hardness and strength. Composite with 4 vol.% titanium diboride sintered at 1100°C resulted in improved hardness and elastic modulus which could be related to Orowan strengthening resulting from homogeneous distribution of fine titanium diboride particles in steel matrix. The results indicate that proposed method is economically feasible to process steel matrix composites with improved properties. A comparatively lower temperature and pressure offers better control of interface kinetics and microstructure.

Effect of Volume Fraction of Primary Alpha Phase on Solid Particle Erosion Behavior of Ti-6Al-4V Alloy

The present article evaluates the influence of independent control factors such as percentage of primary alpha phase, impact velocity, impingement angle, and erodent size on solid particle erosion behavior of Ti-6Al-4V alloy using a statistical approach. Microstructural variation in terms of different percentage of primary alpha phase of investigated alloy has been introduced by solution annealing it at different temperatures followed by thermal aging. Solid particle erosion tests have been carried out using a sand blast–type test rig following an experimental schedule based on Taguchis orthogonal arrays. It is observed that erosion rate and the value of percentage elongation decreased with an increase in the content of primary alpha phase from 10 to 20% and then increased for the value corresponding to the content of 30% primary alpha phase in this alloy. We observed that the solid particle erosion behavior of the investigated alloy consisting of various percentages of primary alpha phase is related to their ductility. Among all four control factors, impact velocity of the erodent has been found to be the most significant control factor influencing the solid particle erosion behavior of this alloy followed by impingement angle, percentage of primary alpha phase, and erodent size. Impact velocity has greatest static influence of 91.35%, impingement angle has an influence of 4.69%, percentage of primary alpha phase has an influence of 2.28%, and erodent size has an influence of 0.42% on solid particle erosion having R2 = 0.99. Material loss during solid particle erosion of this alloy was found to be ductile in nature. Ploughing or pile-up leading to platelet formation is the primary mechanism of material loss during erosion of the alloy.