TiC Inclusions Research Articles

Influence of Ti/N Ratio on Inclusions, Microstructures, and Toughness in Heat‐Affected Zone of Shipbuilding Steel Plates with Mg Deoxidation after High Heat Input Welding

The inclusions, microstructures, and toughness in heat‐affected zone (HAZ) of the shipbuilding steel plates with Mg deoxidation and the different Ti/N ratios are studied after the high heat input welding of 400 kJ cm−1. With increasing the Ti/N ratio from 3.00 to 5.67, the average size of inclusions increases, the mass fraction of total TiC inclusions increase from 2.8% to 5.0%, and the average size of MgO–TiN–MnS increases from 2.82 to 5.49 μm, while the number density that can induce intragranular acicular ferrite (IAF) nucleation decreases from 87 to 62 mm−2. These changes in inclusions are detrimental to induce the IAF nucleation. The HAZ microstructures are composed of the IAFs, polygonal ferrites, and upper bainites (UBs). With increasing the Ti/N ratio, the area fraction of the IAFs decreases from 44% to 14%, and the area fraction of UBs increases from 1.8% to 9.5%. The HAZ fracture mode changes from ductile fracture to brittle fracture after the high heat input welding of 400 kJ cm−1, and the HAZ toughness decreases from 183.3 to 48.7 J at −20 °C.

A 3D characterization of equiaxed grains induced by mediated nucleation in additively manufactured Inconel 718

In additive manufacturing of Ni-based alloy IN718, what causes Icosahedral Short-Range Order (ISRO) or iQC mediated nucleation of equiaxed grains is still not understood. In order to have a better comprehension of the microstructure formation, a more comprehensive characterization both on grain structure and chemical heterogeneities must be achieved. In this work, a scanning electron microscope equipped with a focused ion beam (FIB) allowed to perform a 3D EDS chemical analysis and EBSD orientation mapping of the volume in an equiaxed grain zone. After the 3D reconstruction of the equiaxed grains has been performed, grain-to-grain orientation analysis allowed to analyze multiple twin boundaries orientation relationships in a volume containing hundreds of grains. Chemical mapping using EDS allowed to identify TiC inclusions from which a five-fold symmetry axis seem to emerge, indicating a potential nucleation site. Such areas were analyzed in transmission electron microscopy (TEM) to investigate the different present phases. The nucleation sequence and potential origin of mediated nucleation are further discussed, opening new prospects for grain refinement in additively manufactured nickel-based alloys.

The Effect of TiO2 in the Ladle Slag on Inclusion in Ti‐Bearing Steel

To improve the castability of Ti‐bearing steel, the knowledge of inclusions formed in liquid steel, affected by the slag composition, must be obtained. In this study, the effect of TiO2 in ladle slag on inclusions in this steel at 1873 K is investigated. Experimental results indicate that Ca–Mg–Al–Ti–O complex inclusions, complex TiN inclusions containing MgO–Al2O3–TiOx cores, Ti–C–S inclusions, and TiC inclusions appear in the steel samples. The cores in TiN inclusions are mainly in the liquid and liquid + spinel fields before slag addition. When the steel reacts with slag containing 0% TiO2 for 1 h, the inclusions in the steel are mostly in the MgO + liquid + spinel and MgO + liquid field and have the highest MgO content. When the steel reacts with slag containing 5%≈20% TiO2 for 1 h, most inclusions are liquid slag + spinel and liquid slag phases. The average liquid fraction in most inclusions is higher than 60%. The ratio of the (mass percentages Ti3+) to (Ti3++mass Ti4+) in most liquid phases is approximately 50%≈70% for these oxide cores. Increasing TiO2 content in slag increases log(), which in turn decreases Mg content in the steel. This decreases MgO content in MgO–Al2O3–TiOx type inclusions.

Study of the Fracture Behavior of TiN and TiC Inclusions in NM550 Wear-Resistant Steel during the Tensile Process

NM550 wear-resistant steel is widely used in large-scale engineering and mining machinery under extremely harsh working conditions. In NM550 steel, the addition of Ti can cause the formation of micron-scale TiN and TiC inclusions, easily triggering cleavage fractures. The fracture behavior and precipitation rule of micron-scale TiN and TiC inclusions on the tensile process in NM550 steel was investigated by scanning electron microscopy, transmission electron microscopy, and energy spectrum analysis combined with thermodynamic theory. The TiN precipitated in the solid–liquid two-phase region at a precipitation temperature of 1710 K, whereas that of TiC was 1158 K along the austenite grain boundary. The sizes of the TiN precipitated in the liquid phase and the TiC precipitated in austenite were both at the micron scale, which is prone to cleavage fracture during the stretching process. Under tensile stress, microcracks were first initiated at the TiN inclusion, which were further separated forming a hole, whereas the TiC inclusion was divided into two sections with a long and narrow gap formed between the substrates. The sizes of the TiN and TiC were related to the cooling rate, Ti, and N contents. The larger the cooling rate and the lesser the Ti and N content, the smaller the TiN and TiC sizes.

The effect of using repetitively pulsed laser radiation in selective laser melting when creating a metal-matrix composite Ti-6Al-4V–B4C

A metal-matrix composite based on Ti-6Al-4V–B4C with TiB, TiB2 and TiC inclusions was successfully obtained as a result of in situ synthesis using repetitively pulsed laser radiation. For the first time, the phase composition of the obtained metal-matrix composite was studied using synchrotron radiation. A comparison of the effect of using continuous and pulsed-periodic radiation in selective laser melting on the microstructure and mechanical properties of coatings was made. The use of repetitively pulsed radiation made it possible to form more uniform structures and to improve the mechanical properties of metal-matrix coatings in comparison with the continuous mode of exposure. It has been established that the use of repetitively pulsed radiation and the formation of TiB2, TiB, TiC phases made it possible to increase the wear resistance of the formed composite by a factor of 6 in comparison with the Ti-6Al-4V metal coating.

Melting at the inter-particle contacts during Spark Plasma Sintering: Direct microstructural evidence and relation to particle morphology

During Spark Plasma Sintering (SPS), electric current passing through the sample can cause specific effects not observed in the absence of current. We present microstructural evidence of the formation of melt at the inter-particle contacts during SPS of mechanically milled Ti–C–3Cu mixtures transforming into TiC–Cu composites. The shape of the composite particles acquired after ball milling is related to inter-particle melting during SPS. Particles with higher width/length ratios show a greater tendency to melt at the contacts. The reinforcing effect of TiC inclusions plays a key role in preserving the initial inter-particle contact areas small, as plastic flow at high temperatures was inhibited.

Microstructures and enhanced mechanical properties of an oxide dispersion-strengthened Ni-rich high entropy superalloy fabricated by a powder metallurgical process

Abstract A Ni46Co22Al12Cr8Fe8Ti3Mo1 high entropy superalloy (Ni46 HESA) was fabricated by a powder metallurgical (PM) process. The composition of the alloy was determined through consideration of its PM processability. The alloy had a density of 7.82 g cm−3, which is lower than that of conventional Ni-base superalloys. The microstructure of the bulk alloy consisted of a face-centered cubic γ matrix and an L12 γ′ precipitate with minor amounts of Al2O3 and TiC inclusions. To leverage the advantages of PM processing, yttria (Y2O3) was added and dispersed in the HESA by mechanical alloying, which enhanced its mechanical properties via oxide dispersion strengthening. The oxide dispersion-strengthened Ni46 HESA containing 1 vol% of Y2O3 had a tensile yield strength of 1155 MPa at room temperature, 880 MPa at 700 °C, and 485 MPa at 800 °C. The excellent mechanical properties at room and elevated temperatures are attributed to solid solution strengthening, precipitation strengthening, dispersion strengthening, and grain boundary strengthening. The contribution of each strengthening mechanism was analyzed quantitatively using experimentally determined microstructural parameters.

Dielektrične karakteristike keramičkih kompozitnih materijala sa metalnom matricom na bazi aluminijuma ojačanom titanijum karbidom

The aim of this research work is to study the dielectric and microwave properties of the three ceramic composites Al2O3-TiC, Al2O3-0.3TiC and Al2O3-0.7TiC. The results obtained show that the effective permittivity increases with the increase in the filling rate of titanium carbide TiC inclusions and their contrasts. As for the classical mixing laws, they make it possible to estimate permittivity for low volume fractions and low contrasts. The values of the real part of the complex permittivity decrease with frequency increase in the two bands X and Ku, while the imaginary part is approximately constant in the X band and takes negative values in the Ku band.

Structure and phase composition of SHS products in titanium, carbon and aluminum reactive mixtures

The TiC + Al binder metal matrix composites were obtained by self-propagating high-temperature synthesis (SHS) in the reactive powder mixtures of titanium, carbon (carbon black) and aluminum. It was found that a steady-state wave combustion occurs when the aluminum powder content in reactive mixtures does not exceed 50 wt.%. Loose SHS cakes obtained during synthesis were crashed and screened to get lumpy, nearly equlaxial composite powders favorable to good flowability necessary for powder application in cladding and spraying of wear-resistant coatings. The synthesis products were studied by scanning electron microscopy, X-ray diffraction (XRD) and local energy-dispersive X-ray spectroscopy (EDX). It was found that the average size of carbide inclusions in the composite structure depends on the content of thermally inert aluminum powder in the reaction mixtures. The titanium carbide lattice parameter determined by XRD turned out to be slightly below the known values for equiatomic titanium carbide. However, no any dependence of the lattice parameter on the aluminum content in composites was found. TiC inclusions in the composite structure were investigated by EDX spectroscopy. Titanium content in the carbide was close to that in equiatomic titanium carbide. Titanium carbide contains up to 2.5 wt.% aluminum in addition to titanium and carbon. Aluminum dissolution in the carbide lattice can influence the lattice parameter.

SHS of “TiC – NiCrBSi binder” composite powders

Phase composition and structure of “TiC-NiCrBSi alloy binder” metal matrix composite powders have been investigated. The composites were synthesized from titanium, black carbon and Ni77Cr15Si3B2 alloy reaction powder mixtures by self-propagating high temperature synthesis (SHS). The composite powders were produced by crushing of SHS cakes. A size of TiC inclusions in NiCrSiB matrix depends on the content of NiCrBSi in the reactive powder mixtures and varies from 7.3 to 1.2 μm.

Development of pore-free Ti-Al-C MAX/Al-Si MMC composite materials manufactured by squeeze casting infiltration

An innovative method of manufacturing of Ti-Al-C MAX/Al-Si MMC composite materials was developed using squeeze casting infiltration of open-porous MAX phase preforms. Self-propagating High-temperature Synthesis (SHS) in microwave-assisted mode was applied for the creation of preforms in the Ti-Al-C system, that were subsequently infiltrated with Al-Si alloy to create dense composite materials. Microstructure and phase composition, structural defects and potential impacts between constituents of manufactured composites were characterized by the means of SEM and TEM microscopies and XRD analysis. No undesired reaction at the interface was observed, but TiC inclusions were identified in the material. Among the mechanical properties, the instrumental Young's modulus and Vickers hardness were established. The hardness and the elastic modulus of the matrix were enhanced 4 to 5 times. Wear behaviour was tested with a “pin-on-flat” method with the reciprocating motion for different load values (0.1, 0.2 and 0.5 MPa) for tool steel counterpart. Wear resistance of the composite material (WR = 1.6–2.3 × 10−4 mm3/Nm) was twofold higher than for the sole matrix (WR = 3.5–4.8 × 10−4 mm3/Nm). The developed manufacturing method allows the effective fabrication of pore-free MAX phase based MMC composite materials, with significantly higher wear resistance than the widely applied Al-Si alloys.

Effect of Ball Valve Component Materials on Wear

Features of the wear of mating parts of ball valves made of heat-resistant cast alloy ZhS-6U and cermet based on uncoated titanium carbide TiC–ZhS6U and with wear-resistant TiN and Zr–Ti–N–C coatings are studied. It is established that wear-resistant coatings based on cermets prevent the emergence of hard TiC inclusions at the friction surface thereby reducing friction pair component abrasive and mechanical wear and decreasing the overall degree of ball valve wear.

PRODUCTION OF COMPOSITE CERAMIC MATERIAL FOR THERMAL SPRAYING

A composite ceramic material has been developed for thermal spraying that permits to increase wear resistance due to introduction of high-chromium steel and molybdenum in its structure, to obtain optimum porosity in the starting charge material while synthesizing FeCrMo – MoS 2 /CaF 2 /С – TiC compositions, to improve technological parameters of powders and thereby increase coefficient of powder usage in spraying, to reduce cost of wear-resistant coating technology. The paper presents characteristics and parameters of the developed material and coating which is based on it. Methodology is based on complex metallographical, X-ray diffraction and electron microscopy investigations of structural elements of composite plasma coatings. Main components of composite particles are solid solutions based on iron, titanium carbides, solid lubricant inclusions in the form of molybdenum disulfide, calcium fluoride, carbon. Presence of such powder particles predetermines obtaining wear-resistant coatings which are rather efficient in case of molecular and mechanical and abrasive wear-out under disadvantageous friction conditions (boundary lubrication or absence of lubrication material, elevated temperature actions). The contemplated powders are characterized by complex geometric shape and developed surface relief of particles. There has been observed a stable distribution of hard carbide phase in volumes of deposited materials and absence of superficial zone with deficit of TiC inclusions that positively influence on working capacity of the investigated wear-resistant coatings. Plasma coatings which have been deposited with the help of FeCrMo – MoS 2 – TiC powders in accordance with the technology developed by authors have better wear resistance in case of dry friction in a steel 45 (coating wear-out is less by 1.2-fold; scoring load is higher by 1.2-fold) than a coating which has been obtained with the help of Ni80Cr20 – 12 % MoS 2 – 50 % TiC powder. In such a case coating adhesive strength is increased by 1.23-fold and and powder cost lower is decreased by 1.5-fold. Thus plasma wear-resistant coatings obtained while using FeCrMo – MoS 2 /CaF 2 /carbon – TiC composite powders are considered as prospective for restoration and hardening of steel parts which are operating under disadvantageous friction conditions.

Effect of the microstructure of SHS powders of titanium carbide–nichrome on the properties of detonation coatings

Experiments are carried out for the self-propagating high-temperature synthesis of TiC–NiCr cermets, implemented in a mechanically activated powder mixture of Ti–C–NiCr in the free combustion mode and under pressure. It is found that an increase in the volume fraction of the binder decreases the size of TiC inclusions in particles obtained by the mechanical grinding of synthesized cermet compacts. A CCDS2000 computerized facility developed at the Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, is used to sputter the coatings. The results of comparison of the characteristics of detonation coatings made from the powders produced in this work and commercial Cr3C2–NiCr powder are given. The prospects of employing the self-propagating high-temperature synthesis of TiC–NiCr powders for the thermal spraying of wear resistant coatings are discussed.

Metal Injection Moulding of Superelastic TiNi Parts

TiNi shape-memory properties are successfully used today for the fabrication of various technical devices. The limited machinability and high cost of TiNi encourage the use of near-net shape production techniques such as metal injection moulding. In this work TiNi alloys tensile test specimens are produced by metal injection moulding from pre-alloyed powders. A binder based on a mixture of polyethylene, paraffin wax and stearic acid is used. Parts with a density of about 96.6% of theoretical density are obtained. Scanning electron microscopy coupled with EDX measurements reveals a microstructure consisting of a TiNi matrix with small Ti4Ni2Ox and TiC inclusions. DSC and X-ray diffraction observations indicate the presence of additional Ni4Ti3 precipitates. The parts exhibit full superelasticity at room temperature even for strains of up to 4%, without the need for additional thermal post-treatments. Ultimate tensile strengths up to 980 MPa are obtained.

Effect of Titanium on the Precipitating Behavior of Inclusions and Corrosion Resistance of Niobium Stabilized 409 Ferrite Stainless Steel

In order to investigate the effect of titanium addition on the precipitating behavior of inclusions and corrosion resistance of niobium stabilized ferrite stainless steel, experiments were conducted in a high frequency vacuum induction furnace for smelting titanium and niobium stabilized ferrite stainless steel in argon atmosphere, and the composition, morphologies and size of inclusions in the samples were investigated. Precipitating behavior of the inclusions and intergranular corrosion resistance of the samples were analyzed by CSLM. Corrosion resistance of the steel in 2% NaHSO3 solution was tested by using electrochemistry comprehensive test instrument. The results show that inclusions in the as cast steel mainly are rectangle TiN, TiC, NbC and complex inclusions with TiN or TiC as core packed by NbC, and their size is about 1~5μm. There are a few nearly spherical complex inclusions with Al-Mg-Si-Ti-O as core packed by TiN, TiC, NbC or their complex inclusions. The spherical inclusions become rectangle with the increase of titanium addition, and the quantities of inclusions which size is larger than 5 μm increase. Precipitates increase during heat treated and grain size of the steel becomes a little smaller with the increase of titanium content in the steel. The grain boundary of the steel becomes stabilization and intergranular corrosion resistance enhances with the increase of titanium content in the steel according to the online analysis results. Passivation current density of the steel becomes smaller and passive potential range becomes wider in 2% NaHSO3 solution at 30°C with the increase of titanium content in the steel which indicates corrosion resistance of the steel being enhanced.

Otimização dos processos de moagem e secagem do pó de alumina/TiC obtido por moagem reativa

A presença de aglomerados em pós cerâmicos é fonte conhecida de heterogeneidade e defeitos nos produtos finais, uma vez que na etapa de sinterização ocorre densificação diferencial dos aglomerados. Assim, o controle de todas as etapas do processamento para obtenção de corpos cerâmicos livres de aglomerados e com microestrutura homogênea é de fundamental importância. Neste trabalho foram avaliadas as condições mais adequadas para reduzir a presença de agregados proveniente da etapa de moagem de alta energia, bem como o controle da etapa de secagem para a obtenção de uma microestrutura com tamanho de grãos pequenos e distribuição homogênea das partículas de inclusões no interior da matriz.

Mechanisms and Kinetics of the Hydrothermal Oxidation of Bulk Titanium Silicon Carbide

Hydrothermal oxidation of bulk Ti3SiC2in continuous water flow was studied at 500°–700°C under a hydrostatic pressure of 35 MPa. The oxidation was weak at 500°–600°C and accelerated at 700°C due to the formation of cracks in oxides. The kinetics obeyed a linear time‐law. Due to the high solubility of silica in hydrothermal water, the resulting oxide layers only consisted of titanium oxides and carbon. Besides general oxidation, two special modes are very likely present in current experiments: (1) preferential hydrothermal oxidation of lattice planes perpendicular to thec‐axis inducing cleavage of grains and (2) uneven hydrothermal oxidation related to the occurrence of TiC and SiC impurity inclusions. Nonetheless the resistance against hydrothermal oxidation is remarkably high up to 700°C.

The FEM simulation of mechanical properties characterization of the stent under the quasi‐static loading/unloading. FEM‐ Simulation zur Charakterisierung der mechanischen Eigenschaften von Stents unter quasistatischer Beanspruchung

AbstractIn this paper, the detailed stress distributions of NiTi stents have been studied. The primary object of this study is to set up a cell model to reveal the cause of crack initiation for stents. Auricchio’s super‐elastic model is used to analyze the essential stent cell. Two different kinds of models are analyzed. One model is the stent without defect and the other model is a stent with defects caused by laser burrs or TiC inclusions. The structural stress distribution is not only related to a specimen without defect but also to the material of a bulge defect. The maximum stresses of the stent without defect are near the knots, while the one with defects possesses the maximum stress near the surrounding of the bulge defect. It was found that cracks/fractures can easily appear within a distance of 1/3 of the knot to knot spacing. In particular, a stent with TiC inclusion defects is likely to fail near the bulge face defect. Our simulations agree with experimental results.

They Came from the Deep in the Supernova: The Origin of TiC and Metal Subgrains in Presolar Graphite Grains

A new formation scenario for TiC and Fe-Ni metal inclusions in presolar graphite grains of supernova origin is described. The mineralogy and chemistry require condensation of Fe-Ni titanides from Fe-, Ni-, and Ti-rich gaseous ejecta, subsequent carburization to make TiC and metal, and encapsulation into graphite. Titanides only condense if Si is depleted relative to heavier elements, which requires α-rich freeze-out and a deep mass cut for the supernova ejecta. This Si-poor core material must remain unmixed with other supernova zones until the titanides condense. This can be accomplished by transport of core ejecta in bipolar jets through the major expanding supernova zone ejecta. If the jets stall in regions dominated by C-rich ejecta such as the C-He zone, where graphite condenses, thermochemically favored in situ carburization of the titanides—either before or during encapsulation into condensing graphite—leads to a TiC-and-metal composite. This scenario agrees with theoretical models and observations of asymmetric core collapse in supernovae that are associated with bipolar jets loaded with iron-peak elements.