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Study of dry sliding wear and corrosion behavior of nanocomposite Al-Si-N coated steel
No full textThe present investigation evaluates the wear and corrosion performance of Al-Si-N coated and uncoated steel substrates. The magnetron sputtering technique was used to develop the optically transparent nanocomposite AlSi-N coating over the steel substrate. The Al-Si-N coating was the composite of a polycrystalline phase of wurtzite (hexagonal) AlN and the amorphous phase of Si3N4. The steel's surface hardness value was enhanced significantly by the Al-Si-N coating. The coated steel exhibited -19 GPa hardness value, whereas uncoated steel has -6 GPa. The wear performance testes of the coated and uncoated steels, examined by the ball on disc tribometer, marks 60% less wear of the coated steel than the uncoated steel at 2 N loads. The coated steel wear out by chipping and pull-out abrasive mechanism. The potentiodynamic polarization study indicates improved barrier property and adhesion of the coating than the passive film on the steel with a similar corrosion current value of -10 nA/cm2. The corrosion performance of the uncoated steel (SS 304) did not deteriorate with the Al-Si-N coating. Our analysis-based observations conclude that the nanocomposite Al-Si-N coating exhibits a unique combination of optically transparency, high wear, and corrosion resistance, making Al-Si-N a potential protective candidate for solar panels, optoelectronic devices, automotive shields, and optical devices
Integrity of Additively Manufactured Alloys and Component to Environmental Degradation
No full textThe corrosion behavior of metals/alloys depends on composition, microstructure, defects of varied length scale, and state of the outermost surface besides environmental factors. The undesirable microstructure consisting of dendritic/columnar structure, high residual strain, dislocation density, solute segregation, secondary phases such as carbides, nitrides, sigma, and chi-phase, grain size, and porosity present in the additively manufactured component change its corrosion characteristics significantly as compared to their conventional wrought or cast form. The aluminum alloys, austenitic stainless steels, Ti-6Al-4 V, Inconel 625 and 718 are few which have been progressively fabricated by the different additive manufacturing (AM) processes and have been subjected to a fundamental understanding with respect to mechanical, corrosion, and metallurgical properties. While a large segment of additive manufacturing research is directed toward the study of the design, process optimization, instrumentation, and evaluation of the mechanical properties, the least attention has been paid to exploring corrosion resistance and its response to various environments. While the corrosion properties of AM components are widely different across geometrical locations as compared to their cast and wrought counterpart, these are further modified by the types of the AM process in use and precursor powders. Various features culminated from the AM can be linked to a specific type of corrosion as they can produce conditions conducive to respective corrosion form. This review analyzed various defects that evolved from the AM process and how they influence corrosion. The manuscript further discusses the susceptibility of AM-processed components to specific forms of corrosion including hot corrosion with emphasis on corrosion protocol developments for AM components
Microstructure Property Correlation of Low Alloy Steel Processed through Heat Treatment
No full textIn the current study, an effort has been made to establish a relationship between the low alloy steel’s
microstructure and properties. Austenitizing temperature of for this low steel was taken at 1150˚C for
1-hour holding for annealing, normalizing, quenching in water and oil. Tempering was done (below
A1) at 550˚C for a two-hour holding period, and then quenched specimens were cooled by air. By using
optical microscopy and SEM, on base specimen ferrite, carbides and early austenite grains (PAG).
Microstructure of the annealing specimen was ferrite + pearlite. Microstructure of the normalizing
specimen was proeutectoid ferrite and fine carbide with bainite. Ferrite + tempered martensite +
carbide precipitates are observed in microstructure of quenched in water followed by tempering of low
alloy steel. Ferrite + bainite + carbide precipitates are observed in microstructure of quenched in oil
followed by tempering of low alloy steel. The mechanical properties of base alloy, annealing,
normalizing, water and oil quenching followed by tempering low alloy specimens are was tested by
Vickers macro hardness, Tensile test (UTS, Y.S, Elongation %) and Charpy impact test are 195.46
HV,150.19 HV, 289.90 HV, 337.33 HV and 289.71 HV; (610.82 MPa, 444.99 MPa, 823.28 MPa, 954.89
MPa and 916.73 Mpa; 492 MPa, 241.41 MPa, 604.74 MPa, 837.04 MPa and 788.15 MPa; 22.07 %,
18.94 %, 12.17 %, 11.84 % and 12.63 %); 85.5 J, 20.67 J, 32.67 J, 25.33 J and 22.67 J respectively.
Fractography of tensile specimens of base alloy and heat treated reveal ductile fracture
Weibull parameter based probability distribution for predicting creep life of power plant materials: A non-destructive approach
No full textThe knowledge of remaining useful life and the probability of failure at any point of time in the life cycle
of any power plant component is an important information for the plant operators to take preventive
action. This paper focuses on life data evaluation of creep-exposed power plant material based on statistical
probability distribution through Weibull analysis. The probability distribution was obtained considering
the change in non-linear ultrasonic (NLU) parameter measured in P92 steel at different creep test
conditions. The material was creep tested at 650⁰C for three different applied stresses. The NLU
parameter (b), which indicates the extent of damage, is the ratio of the amplitude of the fundamental frequency
of the transmitted signal to the square of the amplitude of the second harmonic of a sinusoidal
wave propagated into the material. The two-parameter based Weibull distribution function was adopted
for evaluating the cumulative distribution function and failure rate. A sudden increase in NLU parameter
was observed at 80% of creep damage followed by a drop in its value indicating the specimen failure.
With increase in applied stress, failure rate increase was also observed. Microstructural observations
revealed that with creep progress, the growth and coarsening of precipitates, micro crack formation
and their coalescence were the major cause for increase in failure rate. Therefore, application of this
technique can be useful for evaluating the creep life and probability of failure of any plant component
in a non-invasive way
Mechanical properties and corrosion behavior of duplex stainless steel weldment using novel electrodes
No full textMechanical and corrosion properties of welded duplex stainless steel (DSS) structures are of paramount consideration in many engineering applications. The current research investigates the mechanical properties and corrosion integrity of duplex stainless-steel weldment in a simulated 3.5% NaCl environment using specially developed novel electrodes without the addition of alloying elements to the flux samples. Two different types of fluxes having basicity indexes of 2.40 and 0.40 were used to coat E1 and E2 electrodes respectively for DSS plate welding. The thermal stability of the formulated flux was evaluated using thermogravimetric analysis. The chemical composition, optical emission spectroscopy, and the mechanical and corrosion properties of the welded joints were evaluated as per different ASTM standards. X-ray diffraction was used to find out the phases present in the DSS welded joints while a scanning electron equipped with EDS was used for microstructural examination of the weldments. The ultimate tensile strength of welded joints made using the E1 electrode was in the range of 715-732 MPa and that of the E2 electrode was found to be 606-687 MPa. The hardness was increased with increased welding current from 90 to 110 A. The welded joint with an E1 electrode coated with basic flux has better mechanical properties. The steel structure in a 3.5% NaCl environment possesses substantial resistance to corrosion attack. This validates the performance of the welded joints made by the newly developed electrode. The results are discussed based on the depletion of alloying elements such as Cr and Mo observed from the weldments with the coated electrodes E1 and E2 as well as precipitation of the Cr2N in the welded joints made by E1 and E2 electrodes
Powder metallurgical processing of CrMnFeCoMo high entropy alloy: Phase evolution, microstructure, thermal stability and mechanical properties
No full textThe outstanding properties of high entropy alloys (HEAs) are attributed to various factors like composition, microstructure, phase formation, synthesis route, etc. In this regard, the present investigation deals with phase evolution, microstructure, thermal stability, and microhardness properties of an equiatomic quinary Cr-Mn-Fe-Co-Mo high entropy alloy synthesized by mechanical alloying followed by pressure-less sintering. The structure and phase evolution with milling time was studied by x-ray diffraction technique. After completion of 40 h of milling, two simple solid solution phases with BCC structure (a = 3.146 +/- 0.002 angstrom and 2.873 +/- 0.002 angstrom) along with a minor amount of undissolved alpha-Mn were identified. Phase formation, chemical composition, thermal stability, etc. were also evaluated using electron microscopy and differential thermal analysis (DTA) methods as well as in-situ high-temperature x-ray diffraction technique. In the sintered sample, four phases consisting of two BCC solid solutions, sigma (sigma) and mu (mu) type phases are observed to coexist and to be stable up to the melting point. The phase formation was predicted by the Thermo-Calc approach and was compared with the experimental observation as well as other calculated results. The sintered samples were tested by instrumented hardness tester for evaluation of mechanical properties and were found to exhibit high hardness (9.3 +/- 0.3 GPa) and Young's modulus (similar to 245 +/- 6 GPa). (c) 2022 Elsevier B.V. All rights reserved
Natural gums as a novel, potent, and natural additive towards coke making: a preliminary feasibility study
No full textThe present investigation entails delineating the implications of using a novel and naturally sourced additive for coke making. In particular, the focus of this study was to understand the extent to which such natural gums could induce plasticity and strength in non-coking coals without the inclusion of any prime coking coal, emphasizing the importance of thermal pre-treatment as an important parameter. Experimentally, the non-coking coal was pre-treated with xanthan gum (300 degrees C for 1 h), followed by carbonization at 600 degrees C for 1 h. The addition of water as an additive was deduced to be beneficial in enhancing the bulk density of the coal blend. The coal blend, including non-coking coal with natural gums (10-20%) and water (10 mL in 20 g scale), produced F-grade coke when treated under low-temperature Gray King (LTGK) assay conditions at 600 degrees C. A comparative XRD and Raman analysis of raw coal and coke demonstrated the presence of graphitic content in the resultant coke only. FTIR results showed the absence of small molecular fragments, thus substantiating semi-coke formation during the re-solidification stage. The present invention holds significant industrial viability toward the production of coke from non-coking coal without the inclusion of any prime coking coal
Experimental characterization of dynamic fracture toughness behavior of X80 pipeline steel welded joints for different heat inputs
No full textStructural integrity of oil and gas pipelines depends on fracture toughness and metallurgical properties of pipeline steel welded joints. Dynamic fracture toughness (J(Id)) is an important parameter to measure structural integrity in terms of fracture toughness of pipeline steel welded joints under impact loading. Welding input parameters such as current (A), voltage (V), and travel speed (cm/m) significantly affect the mechanical and metallurgical properties of the weldments; therefore, to study the cumulative effect of these parameters, author(s) used different heat input (kJ/cm) as an input parameter in the present work. In the present work, three different levels of heat input such as low heat input (LHI)15 kJ/cm, medium heat input (MHI)20 kJ/cm, and high heat input (HHI) 25 kJ/cm were employed for the fabrication of X80 pipeline steel welded joints. Thereafter, mechanical and metallurgical behavior of different locations (Fusion line (FL), FL + 1 mm, FL + 2 mm, and FL + 3 mm) in multi-pass X80 pipeline steel weld joint was investigated under cold climatic conditions (- 20 degrees C). The dynamic fracture toughness was measured from instrumented Charpy impact test results using three different estimation methods. Furthermore, a finite element model was developed to simulate the Charpy impact test and validate the experimental results, using the Johnson-Cook constitutive model
Interpretation of induction time and particle recovery in a microstructured counter-current flow column
No full textLow-grade coal is in abundance, which is used in most thermal power plants, cement units, metallurgical plants, etc., and creates environmental pollution because of the generation of large amounts of fine solid particles and gaseous pollutants. Therefore, it is of utmost importance to clean coal before use. The present work reports the particle recovery and bubble-particle induction times based on the demineralization of coal particles using the column flotation beneficiation technique in a microstructured flotation column. The effect of operating variables on particle recovery, flotation rate constant, efficiency index, ash content, combustible recovery, and induction time is studied. Induction time is enunciated using the phenomenological kinetic model, which is based on the consecutive sub-processes comprising bubble-particle collision, attachment, and detachment. The results showed a shorter induction time and a higher rate constant at higher particle recovery. The flotation system was optimized by varying the collector as well as surfactant doses, and the maximum efficiency index was found to be 47.70%, with 91.88% combustible recovery and 12.53% ash content in the concentrate at 0.020 m/s feed and 0.082 m/s gas velocity. The induction time was observed to vary from 8.68 to 16.6 ms
On the importance of local equilibria in alloy design criteria for bulk nano-pearlitic steels and ensuing mechanical properties
No full textA critical review of the dependence of yield strength of pearlite on interlamellar spacing unveils the contribution of solid solution strengthening of ferrite. In order to understand the evolution of solute content within pearlitic ferrite, importance of various local equilibria modes (assumed to persist during transformation) has been realized and revisited in present work. With this understanding, an alloy composition and corresponding two stage cooling process have been designed to have nano-pearlitic microstructure (interlamellar spacing < 100 nm). Characterization of elemental partitioning across the growing pearlite-austenite interface using scanning trans-mission electron microscopy coupled with energy dispersive x-ray spectroscopy (STEM-EDS) reveals no-partitioning growth mode of pearlite. Further, mechanical properties have been assessed for samples inter-rupted during cooling post pearlite formation (at 635 ?, S-635) and for those cooled till room temperature (S-RT). Reduction in ferrite width from-70 nm to-65 nm along with increase in post transformation enrichment of pearlitic ferrite with Si from S635 and SRT, has been shown to lead to an increase in the yield strength from-680 MPa to-775 MPa in the deigned alloy