Characterization of Fe–C–Cr Based Hardfacing Alloys

Hardfacing is one of the adaptable methods that can build up the hard and wear resistant surface layer of different materials on the surface of substrate material. It helps them withstand wear, as well as prevent corrosion and high temperature oxidation. In the present investigation three different types of Fe–C–Cr based hardfacing electrodes with varying chemical compositions were deposited on ASTM A36 steel substrate by using manual metal arc welding (MMAW) process. ASTM A36 steel was selected as a base material after consulting with Pressure and Process Boilers, Saharanpur (India), which is a leading manufacturer of boilers. ASTM A36 steel is mostly used by this company for the production of induced draft fans. MMAW process with direct current constant current type power source was used to deposit the hardfaced layers of uniform quality. Straight polarity was used for MMAW process so that more of the arc heat should be concentrated on the electrode. The hardfaced samples were characterized using various characterization techniques and the results of the same were also outlined in the present investigation.     

Microstructure and Wear Performance of ECAP Processed Cast Al–Zn–Mg Alloys

In the present investigation, wear performance of equal channel angular pressing (ECAP) processed cast Al–Zn–Mg alloys under dry sliding wear conditions was studied against a steel disc. Initially, Al–Zn–Mg alloys (with 5, 10, 15% zinc and 2% magnesium) were ECAP processed. After ECAP, grain size was reduced and enhancement in the hardness was observed. Wear resistance of the alloys increased after ECAP processing. Wear resistance of the alloys also increased when the quantity of the zinc was increased in the alloys. But, wear resistance of all three alloys decreased with increase in the load and the sliding speed. Coefficient of friction of the alloys decreased after ECAP processing. Coefficient of friction of the alloys also decreased when the quantity of the zinc was increased in the alloys. Coefficient of friction of all three alloys increased with increase in the load and the sliding speed. Irrespective of the alloy composition and applied load, worn surfaces of the cast and homogenized samples were composed of plastic deformation, scratches and micro-ploughing. On the other hand, in ECAP processed samples, morphology of the worn surfaces depended on the applied load. Abrasive wear is the main wear mechanism perceived in cast and homogenized samples at all loads. While in ECAP processed samples, the wear mechanism shifted from adhesive and oxidation wear to abrasive wear with increase in the load. Formation of oxide layers on the surface of the sample increased with increase in the ECAP passes. In ECAP processed samples, transfer of iron content from the disc to the sample surface was identified.     

Comparison of the Effect of Ni,Mn, Fe,and Si Additives on the Microstructure and Phase Composition of Hypereutectic Aluminum–Calcium Alloys

Russian Journal of Non-Ferrous Metals - A comparative analysis of the phase composition and morphology of primary crystals in hypereutectic alloys of the Al–Ca–Ni–X system (where...     

Spontaneous Pulverization Action of Mn–Al–Fe–Si Alloys and Effect of Addition Ti on the Stability

Systematical experiments have been carried out to investigate the mechanism of cracking and disintegration in the Mn–Al–Fe–Si master alloys. It revealed that pulverization of this alloy is due to the internal stress caused by volume change and hydrolysis. The earlier volume change associated with both the phase transition of Mn-content phase and the solidification process of ζ-FeSi₂ led to micro cracks. Through the micro cracks channel, the further volume change took place due to the Al₂O₃ expansion which was produced by the hydrolysis of aluminum phosphide and carbide when they contacted air. The two steps interacted with each other and led to complete disintegration of the alloys together. However it has been found that Ti can prevent the alloy hydrolysis due to the formation of stable titanium phosphide and carbide instead of the unstable aluminum phosphide and carbide, but it can not stop the earlier volume expansion.     

Review of Microstructure Evolution in Hypereutectic Al–Si Alloys and its Effect on Wear Properties

Al–Si alloys with silicon content more than 13 % are termed as hypereutectic alloys. In recent years, these alloys have drawn the attention of researchers due to their ability to replace cast iron parts in the transportation industry. The properties of the hypereutectic alloy are greatly dependent on the morphology, size and distribution of primary silicon crystals in the alloy. Mechanical properties of the hypereutectic Al–Si alloy can be improved by the simultaneous refinement and modification of the primary and eutectic silicon and by controlling the solidification parameters. In this paper, the effect of solidification rate and melt treatment on the evolution of microstructure in hypereutectic Al–Si alloys are reviewed. Different types of primary silicon morphology and the conditions for its nucleation and growth are explained. The paper discusses the effect of refinement/modification treatments on the microstructure and properties of the hypereutectic Al-Si alloy. The importance and effect of processing variables and phosphorus refinement on the silicon morphology and wear properties of the alloy is highlighted.     

Effect of Mn Content on Microstructure and Mechanical Properties of Fe–Mn–Cr–C High-Manganese Steels Produced Using Laser-Directed Energy Deposition

The microstructure and mechanical properties of high-manganese steel (HMnS) fabricated using laser-directed energy deposition (LDED) with Fe–Mn–4Cr–0.4C alloys with Mn contents of 13, 18.5, and 24 wt% are investigated. Additionally, the effect of annealing heat treatment on the microstructure and mechanical properties of the deposited HMnS is examined. Regardless of the manganese content, the deposited HMnS exhibits a fine microstructure without any defects (cracks or voids) and a strong fibrous texture along the <001>//building direction of the primary austenite phase. In addition, regardless of the manganese content, the grain size increases during annealing heat treatment, and the hardness decreases as the annealing temperature increases. The strength tends to decrease as the Mn content increases in the as-built state. In addition, regardless of the Mn content, the yield strength and ultimate tensile strength tend to decrease owing to the effect of annealing heat treatment. Although the maximum elongation of 18.5Mn and 24Mn does not change significantly upon heat treatment, the maximum elongation of 13Mn is greatly reduced by annealing. The deformation behavior of HMnS is characterized by transformation-induced plasticity (TRIP) for 13Mn and both TRIP and twinning-induced plasticity for 18.5Mn and 24Mn.     

Microstructure–Wear Resistance Correlation and Wear Mechanisms of Spark Plasma Sintered Cu-Pb Nanocomposites

The dispersion of a softer phase in a metallic matrix reduces the coefficient of friction (COF), often at the expense of an increased wear rate at the tribological contact. To address this issue, unlubricated fretting wear tests were performed on spark plasma sintered Cu-Pb nanocomposites against bearing steel. The sintering temperature and the Pb content as well as the fretting parameters were judiciously selected and varied to investigate the role of microstructure (grain size, second-phase content) on the wear resistance properties of Cu-Pb nanocomposites. A combination of the lowest wear rate (~1.5 × 10^?6 mm³/Nm) and a modest COF (~0.4) was achieved for Cu-15 wt pct Pb nanocomposites. The lower wear rate of Cu-Pb nanocomposites with respect to unreinforced Cu is attributed to high hardness (~2 to 3.5 GPa) of the matrix, Cu₂O/Fe₂O₃-rich oxide layer formation at tribological interface, and exuding of softer Pb particles. The wear properties are discussed in reference to the characteristics of transfer layer on worn surface as well as subsurface damage probed using focused ion beam microscopy. Interestingly, the flash temperature has been found to have insignificant effect on the observed oxidative wear, and alternative mechanisms are proposed. Importantly, the wear resistance properties of the nanocomposites reveal a weak Hall–Petch-like relationship with grain size of nanocrystalline Cu.     

Effect of Cr and Ni/Fe Ratio on the Microstructure and Mechanical Properties of γ′-Strengthened Ni–Fe-Based Alloys

Metallurgical and Materials Transactions A - To continue to meet the future materials’ requirements for advanced power generation systems, enhancing the mechanical properties and long-term...     

High Temperature Friction and Wear Characteristics of Fe–Cu–C Based Self-Lubricating Material

The objective of this paper is to investigate the tribological properties of a novel iron-copper-graphite (Fe–Cu–C) based self lubricating material at high temperature. The effect of Calcium fluoride (CaF₂) as a solid lubricant on friction and wear behavior of sintered Fe–Cu–C materials has been studied. Fe–Cu–C based self-lubricating materials were prepared by single stage compaction and sintering process. CaF₂ was added to Fe–2Cu–0.8C based materials in different weight percentages of 0, 3, 6, 9, and 12 wt%. The developed materials were tested for mechanical and tribological properties at high temperature (500 °C). The worn out surfaces were analyzed using a scanning electron microscope. The material with 3 wt% CaF₂ exhibited high hardness value where as compression strength of the materials decreased with the addition of CaF₂. Samples with 3, 6, and 9 wt% exhibited low value of coefficient of friction (COF) than base matrix. The material with 3 wt% CaF₂ addition exhibited better wear resistance as compared to other developed materials. The worn surfaces were mostly characterized by delaminating and abrasive wear. A high temperature solid lubricant CaF₂ was used in Fe–Cu–C based matrix and, the developed composites were tested for tribological properties at high temperature. The results showed that addition of CaF₂ in Fe–Cu–C improved the friction and wear properties. Based upon the findings, the developed material could be used for antifriction applications.     

Surface Oxidation and Wettability of Fe–Mn and Fe–Mn–Si-Alloyed Steel After Annealing

Metallurgical and Materials Transactions A - The surface oxidation and wettability of Mn and Si-alloyed steel after annealing at different conditions are studied with scanning electron microscope...     

Investigation of the Thermal and Electrical Properties of Al–1.9Mn–xFe Ternary Alloys

Russian Journal of Non-Ferrous Metals - In this work, the thermal conductivity, electrical conductivity, enthalpy of fusion, specific heat capacity and thermal diffusivity of the...     

Regularities of Formation and Degradation of the Microstructure and Properties of New Ultrafine-Grained Low-Modulus Ti–Nb–Mo–Zr Alloys

Abstract—Regularities of the formation of ultrafine-grained (UFG) and submicrocrystalline (SMC) structures in new nickel-free low-modulus Ti–Nb–Mo–Zr titanium β alloys under the action of plastic deformation have been studied. Temperature–time ranges of the development of dynamic recrystallization processes under the simultaneous action of temperature and plastic deformation are determined. A type-II recrystallization diagram of the Ti–28Nb–8Mo–12Zr alloy is constructed and analyzed. It is shown using scanning electron microscopy and the electron backscatter diffraction method that the UFG structure with an average grain size of no more than 7 μm and high fraction of high-angle grain boundaries is formed in the investigated alloys as a result of longitudinal rolling, followed by annealing for quenching. It is found that the formation of the UFG structure leads to a significant increase in the strength and plastic characteristics of these alloys. The regularities of the formation of UFG and SMC structures in titanium β alloys Ti–28Nb–8Mo–12Zr and industrial VT30 under the action of plastic deformation by the helical rolling method are studied. It is shown that the helical rolling of the VT30 alloy leads to the formation of the homogeneous UFG state as opposed to the Ti–28Nb–8Mo–12Zr alloy, where this method causes structure softening with micropores and microcracks formed in the central region. It is possible to form a nanostructured state with an average grain size of about 100 nm in Ti–Nb–Mo–Zr titanium β alloys using the high-pressure torsion method.     

Weldability and Microstructure of Nickel-Silicon Based Alloys

The NiSix based alloy typically has poor weldability due to its lower ductility. A limited amount of work has been performed on the weldability of NiSix based alloys. Therefore, the effect of heat treatment and welding parameters on weldability of the alloys, and the relationship between the weldability and microstructure were studied. The results show that the as-cast Ni-Si-Nb-B alloy （Ni 76. 5%, Si 20%, Nb 3%, and B 0. 5%） could be successfully welded after preheating at 600 ℃. The welding procedure should be performed on the alloys before any heat treatment and a preheating at 600 ℃ should be used. The fusion zone is harder than the matrix due to a large amount of 7 phase and a finer microstructure. The cracks are predominantly intergranular in heat affected zone and associated with the needle-like ）, phase. The heat treatment before welding increases the tendency of cracking in the fusion zone.