Faculty Publications
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Item Microstructural and Hardness evolution of AZ80 alloy after ECAP and post-ECAP processes(Elsevier Ltd, 2018) Naik, G.M.; Gote, G.D.; Narendranath, S.This research paper investigates the microstructure evolution and hardness variation of wrought AZ80 magnesium alloy after each ECAP passes. The strengthening effect of AZ80 alloy was examined after post-ECAP aging treatment. Alloys were severely deformed through equal channel angular press at 533K using route Bc with a die channel angle (φ) 1100 and corner angle (ψ) 300. Subsequently, the microstructural characterization was studied using optical microscope (OM) and scanning electron microscope (SEM). Further, post-ECAP aging treatment at 523K for 6h and 12h was performed and microhardness of the specimens was measured. It was found that the grain refinement through thermo-mechanical processing of ECAP and Post-ECAP treatment significantly improves the microhardness of the Mg alloy, which directly influences the properties of wrought AZ80 magnesium alloy. © 2018 Elsevier Ltd. All rights reserved.Item Effect of cryogenic diamond burnishing on residual stress and microhardness of 17-4 PH stainless steel(Elsevier Ltd, 2018) Sachin, B.; Narendranath, S.; Dupadu, D.Diamond burnishing is a cold working process, which produces a work hardened and uniform surface by plastic deformation. The aim of the present work is to study the behavior of diamond burnishing on surface integrity of 17-4 precipitation hardenable stainless steel (PH-SS) under cryogenic, minimum quantity lubrication (MQL) and dry environments. Surface modification was achieved by the application of liquid nitrogen during diamond burnishing. The process parameters considered were speed, feed, burnishing depth and number of passes. Surface integrity characteristics such as microhardness and residual stresses were investigated after diamond burnishing under cryogenic, MQL and dry environments. In cryogenic diamond burnishing, the surface integrity characteristics of 17-4 PH stainless steel has been significantly improved when compared to MQL and dry environments. Maximum microhardness of 395 HV, 369 HV, and 357 HV respectively was observed under cryogenic, MQL and dry environment. The maximum residual stress of -352 MPa, -282 MPa and -195 MPa respectively were recorded for cryogenic, MQL and dry environment. © 2018 Elsevier Ltd. All rights reserved.Item Effect of retrogression and re-ageing heat treatment on microstructure and microhardness of aluminium 7010 alloy(EDP Sciences edps@edpsciences.com, 2018) Nandana, M.S.; Udaya Bhat, K.; Manjunatha, C.M.Aluminium alloy 7010 is subjected to retrogression and re-ageing (RRA) heat treatment to study the influence of microstructural changes on hardness. Retrogression is performed at 190 °C for different time intervals ranging from 10 to 60 minutes. Optimum time for retrogression treatment is estimated based on the retrogression time that result with equivalent mechanical properties as that of peak aged (T6) condition. Retrogression performed for 30 minutes resulted with micro hardness of 203 HV, which is equivalent to that obtained by following T6 treatment. Microstructural characterization done with the help of transmission electron microscope (TEM) indicates RRA treatment results with the coarsened and discontinuous precipitates along the grain boundary which is similar to over aged (T7) condition, where as fine and densely populated precipitates in the matrix similar to T6 condition. Coarse and discontinuous grain boundary precipitates (GBP's) improves resistance to stress corrosion cracking. Fine and dense precipitates in the matrix ensures hardness equivalent to that of T6. © The Authors, published by EDP Sciences, 2018.Item Plasma-sprayed graphene oxide reinforced alumina composite coatings on low carbon steel with improved fracture toughness, brittleness index, and microhardness(Elsevier Ltd, 2020) Amudha, A.; Nagaraja, H.S.; Shashikala, H.D.In this work, the mechanical properties of atmospheric plasma-sprayed Al2O3and Al2O3-xGO (x = 0.5, 1.0, 1.5, and 2.0 wt%) coatings on low carbon steel was evaluated using the Vickers indentation technique, and the effects of GO addition in microhardness brittleness index and fracture toughness were investigated. The Fourier-transform infrared (FTIR) spectroscopy and Field Emission Scanning Electron Microscopy (FE-SEM) techniques were employed to analyze the microstructural characterization of the plasma-sprayed coatings and to confirm the retention of GO in the Al2O3-xGO composite after the plasma spray. It was found that the Vicker's microhardness of as-sprayed Al2O3is 4.148 GPa and it decreased with the increase in the addition of GO and for Al2O3-2.0GO, it is 3.305 GPa. The fracture toughness of Al2O3is 4.86 (MPa m1/2) whereas for Al2O3-2.0GO is 16.85 (MPa m1/2). The fracture toughness has increased whereas the brittleness index has decreased as the weight percentage of GO addition is increased in the Al2O3-GO composite. Thus, the plasma-sprayed Al2O3and Al2O3-xGO coatings suggest that 2 wt% GO addition helps in the improvement of brittleness, fracture toughness, and the microhardness. © 2020 Elsevier Ltd. All rights reserved.Item Effect of wire feed rate on microstructure development during bead on plate welding of microalloyed steel using P-GMAW(Elsevier Ltd, 2020) John, M.; Kumar, P.A.; Udaya Bhat, K.Welding of advanced high strength steel has been challenging because of difficulties associated with retaining high strength and toughness in the weldment. In this investigation, Ti-Nb microalloyed 800 MPa steel was subjected to bead on plate welding trials using ER70S-6 filler wire. Synergic pulsed mode was used for welding. Here the system could optimize the welding current and voltage once the selection of wire feed rate was done. Analysis of weld bead was done by measuring the weld bead parameters, observing microstructural details and calculating microhardness values. The investigation indicates that 6 m/min wire feed rate produces good weld bead, minimum reinforcement and optimum dilution. The microstructure is predominantly acicular in nature and microhardness in weld and HAZ is higher compared to the beads produced using other wire feed rates. © 2020 Elsevier Ltd. All rights reserved.Item A study on HAZ behaviour in 800 MPa cold rolled and hot rolled steel weld(Elsevier Ltd, 2021) John, M.; Perka, P.; Udaya Bhat, K.; Bhat Panemangalore, D.In the automotive sector, the demand for advanced high strength steels (AHSS) is increasing day by day. Based on the application, cold rolled and hot rolled steels are used for various components in a vehicle body. Typically, cold-rolled grades with dual-phase, DP780 steel is used in the form of welded blanks. Hot rolled grades with Ti-Nb microalloy content, like HS800 steel are used in as long members. Welding is an important step to be considered in the design of materials for mass production as required in the automobile sector. In this investigation, Pulsed Gas Metal Arc Welding (P-GMAW) is carried out on both steels with a solid filler wire of strength 800 MPa. Static tensile tests indicated that failure in both steels welds occurred in the heat-affected zone region. The crack initiation and propagation behaviour were compared in both steels. In DP780 steels, the presence of the acicular ferrite and acicular martensite resisted the crack initiation and propagation in the weld region whereas, the chaotic nature of the acicular ferrite in HS800 steel. Microstructural studies revealed that the reason for heat affected zone (HAZ) failure in HS800 steel is due to the presence of hard TiN particles with a size of more than 1 µm which causes decohesion in the matrix. In DP780 steel failure is due to the presence of tempered martensite in the subcritical heat affected zone (SCHAZ). This study divulges the influence of filler wire chemistry, dilution, and welding parameters on cold rolled and hot rolled AHSS steels used in the automotive industry. © 2021 Elsevier Ltd. All rights reserved.Item Compositionally modulated multilayer Cu-Zn alloy coatings fabricated using eco-friendly non-cyanide pulse electrochemical deposition(Elsevier Ltd, 2023) Bharadishettar, N.; Kumar, K.; Udaya Bhat, K.Pulse electrodeposition of Cu-Zn compositional modulated multilayer alloy (CMA) coatings was carried out onto AISI 304 stainless steel substrate using an environmentally friendly alkaline non-cyanide electrolytic bath. Cu-Zn alloy multilayer coating was co-electrodeposited using a trapezoidal pulse current. Multilayer coatings can have two different metals in layers or two-phase mixtures. Different sets of multilayers of 10, 20, 50, and 100 were done using a trapezoidal pulse current. In the trapezoidal pulse current module, during the higher current stage (0.1 A) Zn was deposited as compared to the lower current module (0.02 A) where Cu was deposited. Microstructural and structural analysis of the coatings confirmed nanocrystalline morphology with peaks corresponding to crystallographic planes of (002), (111), (020), and (022). Deposited coatings are hydrophilic in nature. The microhardness of the coatings is decreased with an increase in the number of layers deposited. © © 2023 Elsevier Ltd. All rights reserved.Item Influence of milling parameters on Al-Li alloy surface characteristics(Elsevier Ltd, 2023) Marakini, V.; Srinivasa Pai, P.; Udaya Bhat, K.; Thakur, D.S.; Achar, B.P.Lightweight alloys attract the aerospace industries due to their high specific strength. Al-Li alloy has been investigated in the present study to identify their functional performance in terms of surface characteristics namely surface roughness and hardness. Dry face milling was performed using uncoated carbide inserts for the experimental conditions obtained from Taguchi L27 design of experiments. The effect of milling parameters, such as feed rate, cutting speed and depth of cut on surface roughness and hardness have been investigated and presented. Further, the optimal milling conditions are identified using statistical techniques – Grey Relational Analysis (GRA) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The study showed that feed rate is the most influential parameter on both surface characteristics. Both GRA and TOPSIS showed similarity in identifying the same condition as optimal for milling Al-Li alloy under dry condition. © © 2023 Elsevier Ltd. All rights reserved.Item Role of zirconia filler on friction and dry sliding wear behaviour of bismaleimide nanocomposites(2011) Kurahatti, R.V.; Surendranathan, A.O.; Srivastava, S.; Singh, N.; Ramesh Kumar, A.V.; Suresha, B.This paper discusses the friction and dry sliding wear behaviour of nano-zirconia (nano-ZrO2) filled bismleimide (BMI) composites. Nano-ZrO2 filled BMI composites, containing 0.5, 1, 5 and 10wt.% were prepared using high shear mixer. The influence of these particles on the microhardness, friction and dry sliding wear behaviour were measured with microhardness tester and pin-on-disc wear apparatus. The experimental results indicated that the frictional coefficient and specific wear rate of BMI can be reduced at rather low concentration of nano-ZrO2. The lowest specific wear rate of 4×10-6mm3/Nm was observed for 5wt.% nano-ZrO2 filled composite which is decreased by 78% as compared to the neat BMI. The incorporation of nano-ZrO2 particles leads to an increased hardness of BMI and wear performance of the composites shows good correlation with the hardness up to 5wt.% of filler loading. The results have been supplemented with scanning electron micrographs to help understand the possible wear mechanisms. © 2011 Elsevier Ltd.Item Role of nickel filler on friction and dry sliding wear behavior of bismaleimide nanocomposite(2011) Kurahatti, R.V.; Surendranathan, A.O.; Srivastava, S.; Singh, N.; Ramesh Kumar, A.V.; Kori, S.A.Nano-sized metal particles filled polymer composites are finding numerous tribological applications in recent years. In the present work, the matrix properties were investigated by introducing nickel (Ni) nanoparticles (60-100 nm, weight fractions of 0.5-10 %) into a bismaleimide (BMI) resin. The influence of these particles on the microhardness, friction and dry sliding wear behavior were measured using microhardness tester, pin-ondisc wear set up. The experimental results indicated that the coefficient of friction and the specific wear rate (SWR) of BMI resin can be reduced at rather low weight fraction of Ni particles. The lowest SWR of 9 ×10 -6 mm 3/Nm (i.e. 50% lower than the value of neat BMI) was observed for the nanocomposite with Ni weight fraction of 1%. The incorporation of Ni particles leads to an increased hardness of BMI and the wear performance of the composites shows good correlation with the hardness. The results have been supplemented with scanning electron micrographs to help understand the possible wear mechanisms. © 2011 CAFET-INNOVA TECHNICAL SOCIETY.