Effect Of Niobium Addition Research Articles

Hybrid modelling of dynamic softening using modified Avrami kinetics under Gaussian processes

This paper presents a new method of modelling that combines several approaches to anticipate the softening of nickel-niobium alloys during dynamic recrystallization (DRX). The study employs an extensive dataset obtained from hot torsion deformation tests conducted on high-purity nickel and six nickel-niobium alloys. The niobium concentration in these alloys varies from 0.01 to 10 wt % (Matougui et al., 2013). The hybrid technique integrates the Avrami model to provide early predictions about the kinetics of recrystallization and then uses mechanistic modelling to assess the progression of softening caused by dynamic recrystallization (DRX). The integrated technique is improved by using Gaussian process regression analysis, which investigates the softening properties and offers useful insights into the effects of niobium additions on dynamic softening behaviour. This unique hybrid framework combines multiple modelling tools to reveal intricate connections impacted by solute addition, therefore enhancing our comprehension of the physical events that take place during the hot deformation of superalloys. The use of empirical, mechanistic, and machine learning methods in this hybrid model provides a more thorough and detailed investigation of DRX processes in these alloys.

Effect of niobium addition on the microstructure and wear properties of mechanical alloyed Cu–Al–Ni shape memory alloy

Abstract In this study, the influence of the addition of Nb in varying amounts (0.5, 1, 1.5, and 2 wt.%) to Cu–14Al–4Ni shape memory alloy on the microstructure and wear behavior of the alloy was investigated. Cu–Al–Ni-xNb alloys were produced from elemental powders using the mechanical alloying (MA) method. The microstructures of the produced samples were examined using SEM + EDS and XRD, and density and hardness measurements were performed. For the wear tests of Cu–14Al–4Ni and alloys containing different amounts of Nb, a pin-on-disk type wear testing device was used with three different loads (10 N, 20 N, and 30 N) and five different sliding distances (400 m, 800 m, 1,200 m, 1,600 m, and 2000 m). As a result of the conducted research, it was determined that an increase in the Nb content resulted in a decrease in the average grain size and a more homogeneous grain size distribution. The highest hardness and density values were measured in the alloy with 2 wt.% Nb addition. In the wear tests, it was observed that the friction coefficients decreased with increasing load, and the lowest wear rate was achieved in the alloy with 2 wt.% Nb addition.

The Effect of Niobium Addition on the Operational and Metallurgical Behavior of Fe-Cr-C Hardfacing Deposited by Shielded Metal Arc Welding

Hardfacing is commonly used in parts recovery and in obtaining surfaces with improved properties. Within this field, it is important to analyze the effect of alloying elements on the properties of the deposited layers. One of the critical parameters affecting alloying performances in SMAW is improper arc length. This article examines the effect of the addition of niobium in different quantities (0, 2, 4, 6, and 8% by weight) to the electrode coating in Fe-Cr-C shielded metal arc welding (SMAW), with short and long arc lengths, on the operational process efficiency, dilution, arc energy, microstructure, and microhardness of the deposited layers. A decrease in operational process efficiency and dilution was found with increases in niobium content. On the other hand, it was found that adding niobium leads to a refinement in chromium carbide sizes, directly affecting the hardness of the obtained deposits. There is a direct relationship between the arc energy, with both short and long arc lengths, leading to a tendency to decrease the dilution in the obtained hardfacing.

The Effect of Niobium Addition and Pre-Annealing on the Tensile Properties of 52CrMoV4 Spring Steel.

In this study, the effect of niobium addition and a specific preheating process on the microstructure and tensile properties of 52CrMoV4 steel used in leaf springs was investigated. Flat and leaf spring materials were used to accomplish this aim. The flat materials under investigation were kept in a furnace for 90 min at 900 °C. A homogeneous microstructure was aimed for with the use of this pre-annealing heat treatment in addition to the standard process before rolling used to create NbC. Leaf spring production was carried out with flat materials that possessed various Nb contents, with or without pre-heating. Grain size measurement and tensile tests were performed on the flat and leaf springs. Additionally, scanning electron microscopy images were captured from the fractured surfaces after the tensile tests were carried out. The current study highlights the importance of Nb addition as an alloying element and the effect of the selected pre-annealing process in optimizing the grain structure and enhancing the tensile properties of leaf springs. The leaf spring with a Nb ratio of 0.0376 that was pre-annealed exhibited a finer grain structure (G = 11.3), greater tensile properties (YS = 1550 N/mm2 and UTS = 1688.6 N/mm2), and deeper tear valleys and larger dimples, indicating higher energy consumption during fracturing, according to the SEM images produced, in contrast with the other materials studied.

Effects of Niobium addition on dynamic mechanical behavior and fracture properties of iron-aluminide-based alloys

The compressive mechanical behavior and fracture characteristics of FeAl intermetallic alloys containing 0–9 at.% Nb were investigated over a wide strain rate range of 10−3 s−1 to 5 × 103 s−1. For all of the alloys, the flow stress and strain rate sensitivity increased with increasing strain rate; however, the fracture strain decreased. The addition of Nb improved both the compressive strength and the ductility of the alloys. Among the various alloys, the alloy containing 6 at.% Nb showed the highest yield stress and fracture strain. The optical microscopy observations and X-ray diffraction results showed that the change in mechanical behavior of the various FeAl–Nb alloys was due mainly to differences in the precipitation of (Fe,Al)2Nb Laves phase. Moreover, a higher level of Nb addition prompted a change in the fracture morphology from a brittle fracture mode to a ductile fracture mode.

Corrosion resistance of niobium-added slag-free self-shielded flux-cored welding overlay in neutral solution

The niobium-added iron-based slag-free self-shielded flux-cored wire was developed and the effect of niobium addition on the corrosion resistance in neutral pH solution was investigated. The carbides, including NbC carbides, primary (Cr, Fe)7C3, and eutectic (Cr, Fe)3C carbides, remain intact after neutral corrosion, but the grain interface is corroded preferably for all the niobium-added welding overlays. The eutectic microstructure of 7.2 wt-% niobium-added welding overlay, which has more grain interface, leads to severe corrosion. When niobium addition reaches 14.4 wt-%, the welding overlay possesses the best corrosion resistance since more NbC carbides are formed, prophase austenite dendrite is precipitated, decreasing the grain interface, and chromium content is increased in the matrix of the hypoeutectic microstructure.

Resistance to High-Temperature Oxidation of Ti-Al-Nb Alloys.

The research presented in this paper concerns the assessment of the resistance to high-temperature oxidation behaviour of a Ti-46Al-7Nb-0.7Cr-0.1Si-0.2Ni alloy and the explanation of the role of niobium during oxidation processes. The basic problem concerned the evaluation of the resistance of the studied alloy to cyclic oxidation in an air atmosphere, with particular attention to the influence of temperature, surface roughness and cooling rate from heating temperature to room temperature. The issue analysed was the effect of niobium addition on the corrosion kinetics as a high-melting element causing improved oxidation resistance, contributing to the reduction in the oxidation rate.

The Effect of Niobium Addition on Mechanical Properties and Corrosion Resistance of a Medical Grade SS316L

To improve mechanical properties, especially elongation, of as-cast medical grade 316L stainless steel, niobium (Nb) was introduced into the alloys, followed by solution heat treatment. Alloying was performed using a 250 kg air induction melting furnace with duplex raw materials and ferronickel. Heat treatment using a solution at 1040 oC, with a holding time of 45 minutes, and water quenching was used. The sample was tested using hardness and ultimate tensile machines. Corrosion tests with simulated body fluids were carried out using media with similar corrosion conditions to human blood. Microstructure observations were performed optically. The results show that the addition of Nb increases the hardness of medical grade 316L stainless steel by 6% compared to the unalloyed steel, both before and after heat treatment. The addition of Nb increases the tensile strength by 8% compared to non-heat treated steel and increases the elongation before and after heat treatment by 8% and 5%, respectively. However, the corrosion rate of the material with Nb is higher than without the addition of Nb. Nb as a carbide former improves the mechanical properties of medical grade 316L stainless steel but adversely affects its corrosion resistance

Effects of niobium addition on active metal and support in Co–CeO2 catalyst for the high temperature water gas shift reaction

Nb promoter was introduced in the Co–CeO2 catalyst to improve its catalytic performance in the high temperature water gas shift (HT-WGS) reaction, which involves the production of hydrogen from waste-derived synthesis gas. Thereafter, the physicochemical properties of the promoter as well as those of the catalyst were investigated using various techniques. Thus, it was confirmed that the Nb promoter affects the key properties related to catalytic performance, including oxygen storage capacity (OSC) and dispersion. To maximize the positive effect of the Nb promoter, we further investigated the effect of the Nb loading amount on the performance of the catalyst. The results obtained showed that the 1.5NbCo catalyst exhibited the highest catalytic performance (XCO = 89% at 450 °C) under very severe conditions (gas hourly space velocity (GHSV) = 637,320 h−1). Additionally, this catalyst exhibited stable activity for 50 h. This its high catalytic performance could be attributed to its high OSC and Co dispersion. Therefore, it is a promising catalyst for hydrogen production via the HT-WGS reaction.

Effects of niobium addition on microstructure and properties of CPM121 powder metallurgy high-speed steel

Effects of niobium addition on microstructure and properties of CPM121 powder metallurgy high-speed steel

Effect of niobium addition upon microstructure and tensile properties of CrMnFeCoNix high entropy alloys

Abstract Nb-doped CrMnFeCoNix (x = 0.2, 0.4, 0.6, 0.8 and 1) high entropy alloys were prepared by vacuum induction melting. The effects of Ni and Nb content on the microstructure evolution and tensile properties of the alloys were investigated. With increasing Ni content, the CrMnFeCoNix alloy changed its structure from a combination of face-centered cubic phase and σ phase to a single face-centered cubic phase. The yield strength, ultimate tensile strength and ductility of CrMnFeCoNix alloys first increased and then decreased with the increase of Ni content. Compared with other CrMnFeCoNix alloys, CrMnFeCoNi0.8 HEA has shown superior mechanical properties, exhibiting a high yield strength (240.9 MPa), ultimate tensile strength (527.5 MPa) and an impressive elongation-to-failure (62.5%). The addition of Nb significantly increased the volume fraction of Laves phase in the CrMnFeCoNi0.8 alloy, which further enhanced the tensile properties of CrMnFeCoNi0.8 high entropy alloys. The yield strength and ultimate tensile strength of the CrMnFeCoNi0.8Nb0.2 alloy were determined to be 406.9 MPa and 662.8 MPa, representing a 68.9% and 25.6% increase over CrMnFeCoNi0.8 alloy.

Effect of niobium addition on tensile properties and oxidation resistance of a titanium-based alloy

Previous research has inadequately elucidated the influence of Nb addition on the tensile properties and oxidation resistance of Ti-based alloys. Herein, the tensile properties and oxidation resistance of Ti–6Al–2Sn–4Zr–2Mo–0.1Si–1.0B–xNb (x = 0, 0.2, and 1.0) alloys were investigated. The oxidation resistance was significantly improved by Nb addition without significantly influencing the tensile properties. The substitution of Ti4+ by Nb5+ in TiO2 and promoted formation of a Sn-rich layer between the oxidation layer and substrate caused an increase in the oxidation resistance, thus highlighting the effectiveness of Nb addition in enhancing the oxidation resistance.

Niyobyum İlavesinin (Bi, Pb)-2223 Bulk Süperiletken Sistemine Etkisi Üzerine Bir Araştırma

Niyobyum (Nb) ilaveli Bi1.85Pb0.35Sr1.9Ca2.1Cu3.1Oδ içeren bir dizi bizmut-tabanlı bulk süperiletken malzemeler, geleneksel katı hal reaksiyon yöntemi ile sentezlendi. Malzemelerin fazları ve mikro-yapısal analizi, X-ışını kırınımı (XRD) ve taramalı elektron mikroskobu (SEM) ile gerçekleştirildi. Niyobyum ilavesinin elektriksel ve manyetik özellikler üzerindeki etkisi, sırasıyla özdirenç ve mıknatıslanma ölçümleri ile belirlendi. Niyobyum ilavesiyle kritik sıcaklıkta önemli bir azalma olmadı. Ayrıca niyobyum ilave edilmiş malzemelerin oda sıcaklığı özdirenci, saf malzemeye kıyasla azaldı. Nb katkılı numunelerin kritik akım yoğunluk değerleri saf numuneninkinden daha düşüktür.

Influence of Niobium Content on the Mechanical Properties and Abrasion Wear Resistance of Heat-Treated High-Chromium Cast Iron

The effect of niobium addition up to 3.4 wt% on the microstructure and mechanical properties of heat-treated high-Cr cast iron containing 13.5 wt% Cr was investigated. Niobium addition caused small hard NbC particles to precipitate within the proeutectic austenite which impede the development of austenite dendrite growth resulting in structure refinement. This austenitic matrix upon heat treatment changed to mainly martensitic one with some retained austenite and reinforced with small amounts of secondary carbides of M7C3 type. It was found that the hardness increased with increasing Nb content due to structure refinement and precipitation of hard NbC particles. These particles caused a depletion of carbon in the austenite matrix and thus most of the austenite was transformed to martensite upon heat treatment. The highest impact value was obtained for the base alloy without Nb addition which could be attributed to the high amount of retained austenite. The high-Cr cast iron alloyed with Nb in the range of 1.55–3.4 wt% showed an increase in hardness without any deterioration in toughness. The wear resistance was significantly enhanced by the presence of hard NbC particles up to 2.52 wt% Nb. Exceeding this optimum amount of addition leads to agglomeration of NbC particles and hence deterioration of the wear resistance through three body abrasion wear mechanism.

Effect of niobium addition on the properties and microstructure of a high chromium cast iron alloy

High chromium cast iron (HCCI) is usually employed in equipment that experience high abrasive wear and therefore requires high resistance. Niobium could be added to these alloys to improve their resistance to wear. This study consisted in addressing the influence of 0.5% and 1.0% of niobium on the microstructure of a 26% Cr and 2.8% C HCCI alloy. Standard samples – without niobium – and samples with 0.5% and 1.0% Nb were melted, cut and then machined into adequate dimensions for tests. Two groups of samples – with and without heat treatment – were analyzed through X-ray Diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), Vickers and Rockwell-C hardness. Carbides Volume Fraction (CVF) was quantified in the heat-treated samples. The majority of NbC carbides were observed to be thin and presented a hook shaped morphology. In addition, it was noted a precipitation of Nb-rich layers around the M7C3 carbides, which could act as a higher hardness coating. There was significant reduction in carbide volume fraction, from an initial 33.3% to 28.1% for the 0.5 % Nb alloy, and further reduction to 24.9% for the 1.0% Nb alloy, it was also noted an alteration on the quasi-eutectic microstructure to a hypoeutectic microstructure. The NbC carbides prevented hardness reduction as a result of lowering the CVF in heat-treated alloys; however, the alloys without heat treatment experienced reductions in hardness. Keywords: Heat treatment, niobium, high chromium cast iron, microstructure. 1

The Effect of Niobium Addition on the Microstructure and Tensile Properties of Iron-Nickel Base A286 Superalloy

The Effect of Niobium Addition on the Microstructure and Tensile Properties of Iron-Nickel Base A286 Superalloy

Effect of niobium addition in grey cast iron: A short review

The effect of alloying element addition in grey cast iron is great interest of materials developers. In the same context, the effect of adding niobium on mechanical properties of grey cast iron is reviewed. Microstructure and hardness test are reviewed to examine the mechanical properties of alloyed grey cast iron. The study indicated that increasing niobium results in increasing hardness due to which wear rate reduces and also reduces the lamellar spacing between the graphite layers. The reduction in lamellar spacing is due to decreases in eutectic temperature with the addition of niobium. Additionally, mechanical properties including hardness and wear resistance were enhanced after adding niobium.

The effect of niobium addition on the microstructure and properties of cast iron used in cylinder head

Cylinder head is one of the most important parts of heated components in the engine, while cracking due to low strength and large residual stress at high temperature is the main failure mode of cylinder head. With the growing demand of good performance and high reliability, gray cast iron with trace alloying element and optimized annealing process are probably effective ways in obtaining suitable materials. The effect of niobium addition on the microstructure and properties of cast iron used in cylinder head is studied in this paper. The results show that, the tensile strength, toughness, fatigue properties and thermal fatigue properties of gray cast iron are improved by adding trace niobium elements. The specimen with 0.20% niobium shows better comprehensive mechanical properties than others. The addition of trace niobium elements can not only refine the graphite, eutectic cell, carbide and phosphorus eutectic, but also reduce the pearlite lamellar space, thus strengthening the matrix. The cylinder head is made by cast iron with 0.20% niobium addition, and the annealing process of thermal aging is optimized. The residual stress of cylinder head can be maintained at a low level by adopting annealing process with higher holding temperature, longer holding time, lower cooling rate and lower outlet temperature. The analysis of microstructure, mechanical properties and residual stress for niobium alloyed cast iron is helpful for solving the cracking problem of cylinder head, and providing scientific basis for improving engine reliability.

Influence of niobium solutes on the microstructural evolution of nickel during hot working

The effect of niobium additions on the microstructural evolution of nickel during hot working was investigated by optical and electron microscopy (SEM-based EBSD, electron backscatter diffraction). For this purpose, a series of wrought model alloys consisting of pure nickel and six Ni-xNb alloys (x = 0.01, 0.1, 1, 2, 5 and 10 wt% Nb) were prepared and tested in torsion to a true strain of 5 within the temperature range of 800 to 1000 °C and at three strain rates of 0.03, 0.1 and 0.3 s–1. The results revealed that the gradual Nb additions led to increasingly smaller grain sizes ranging from 800 to 40 μm and even up to 1 μm for the gripping area (undeformed head) and the gauge-length (deformed part) of the specimens, respectively. However, a saturation effect was observed at 5−wt% Nb in both cases. If the deformed Ni alloys containing 10-wt% Nb led to unsatisfactory results (in terms of volume fraction and recrystallized grain size) owing to low formability, however, under specific conditions of deformation, some of them gave good results comparable to those containing 5-wt% Nb. Overall, the gradual Nb additions affected, in complex ways, the kinetics and the nature of mechanisms of dynamic recrystallization (DRX) that turned out to be discontinuous dynamic recrystallization (DDRX), continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX) operating separately and/or simultaneously, along with twinning as an additional mechanism.

Effect of Niobium Addition on the High-Temperature Oxidation Behavior of 22Cr25NiWCoCu Stainless Steel in Air

The oxidation behavior of 22Cr25NiWCoCu stainless steel with 0–0.86 wt.% Nb addition was investigated at 900 °C in air. With an increase in Nb addition, the volume fraction and average particle size of Nb (C, N) increased, but the grain size decreased. The results of grazing incidence X-ray diffraction indicated that the steels with Nb additions promoted Cr2O3 formation. After 10–100 h of oxidation, Cr depletion occurred at the region with Nb (C, N) precipitates because of its high Cr consumption rate, leading to Fe oxide generation. Finally, after 100 h of oxidation, the outer layer of Fe2O3 and the inner layer of (Cr, Fe, Mn)3O4 were formed.