Gleeble Testing Research Articles

Effect of Tungsten on Mechanical Properties of High-Purity 60 mass%Cr-Fe Alloys

The effect of the tungsten addition on the mechanical properties of high-purity 60 mass%Cr-Fe alloy was investigated. High-purity 60 mass%Cr-Fe-4 mass%W alloy ingots were prepared by melting in a newly designed high-frequency induction furnace equipped with a cold copper crucible. The purity of the ingots were higher than 99.98 mass% after the analysis of 21 elements. The deformability at temperatures of 1273 to 1573 K and the tensile properties between 293 K and 1073 K were measured by Gleeble test and tensile test. It was found that the tensile strength of 60 mass%Cr-Fe-4 mass%W alloy is higher than that of 60 mass%Cr-Fe alloy, and the addition of tungsten is effective in improving tensile properties of a 60 mass%Cr-Fe alloy.

改良型ＨＰ系耐熱鋳鋼の経年使用材の補修溶接割れ ３ 補修溶接部における高温割れ発生機構

Mechanism of hot cracking, especially ductility-dip cracking in HAZ during repair welding was investigated using modified HP-type heat-resistant cast alloys. The change in hot ductility was evaluated with the reduction of area at 773 K by the Gleeble test. The hot ductility of each alloy was almost at the level of 20% in as-cast situation, while decreased with aging and fell down below about 8% after service exposure or long term aging at elevated temperature. Microscopic observation revealed that the brittle fracture occurred in service exposed alloys, and that cracks initiated and propagated preferentially through microconstituents. Hot ductility was decreased remarkably with increasing the amount of microconstituents on dendritic boundary, and with proceeding the phase transformation of microconstituents as NbC → η phase or M23C6→G phase. It was deduced that the hot ductility would be deteriorated by the stress concentration in microconstituents and/or the plastic constraint on dendritic grain due to the formation of continuous network of microconstituents surrounding the dendritic boundary. It follows that ductility-dip cracking susceptibility during repair welding was enhanced by the reduction of hot ductility.

High-Temperature Mechanical Properties of a High-Purity Cr–Ni Alloy

A high-purity Cr-50 mass%Ni alloy was melted in a cold copper crucible by high-frequency induction heating. Mechanical properties were clarified between 1073 and 1523 K using a Gleeble Testing Machine. The strain rate was 10 s -1 . The microstructures of specimens after heat-treatment and tensile-testing, at various temperatures, were observed by optical microscopy. It was found that a highly purified Cr-50 mass%Ni alloy possesses excellent high-temperature properties, such as strength and ductility up to 1300 K.

Castability of directionally solidified nickel base superalloys

Grain boundary cracking during directional solidification of columnar grained nickel base superalloys has been investigated. A quantitative test has been developed that allows a classification of the castability of directionally solidified nickel base superalloys: CM247LC showed excellent castability, while IN792 showed severe cracking. The cracking was found to originate at a temperature near the solidus temperature (hot tearing). A number of experimental alloys based on the composition of IN792 were tested, with the effects of variations in hafnium, aluminium/titanium, carbon, boron and zirconium contents being examined. A combination of 0%B and 0·01%Zr shows significant promise. A number of approaches were applied to explain the cracking susceptibility. A relationship was found between a small nil ductility region, obtained by Gleeble testing, and good alloy castability for IN792 and CM247LC. A correlation between the eutectic content of the alloy and its cracking tendency was also found. At low (<5%) and high (>22%) amounts of eutectic, a significant reduction in cracking was apparent, while with intermediate amounts (15%), severe cracking was observed.

Microstructure and Mechanics Interaction in the Modeling of Hot Rolling of Rods

During hot metal working, strain, strain rate, temperature, microstructure and chemistry along with associated metallurgical phenomena such as strain hardening, dynamic recovery and recrystallization are known to have a significant effect on the flow stress of the metal. Simple flow stress models such as the power law were found to be inadequate for the accurate prediction of leads and metal flow using numerical simulation. In this study, a microstructure dependent flow stress model was developed by performing uniaxial compression tests on the Gleeble test machine. This model was implemented, using a computationally efficient procedure, into the finite element method based metal flow simulation model for hot rolling. Reasonably good agreements were obtained in comparing predicted rolling loads and rod geometry with those measured on a multi-pass production mill.

Weld heat affected zone liquation cracking in type 347 stainless steel

The heat affected zone cracking-tendency of type 347 stainless steel was evaluated in five different samples of thick walled pipe or plate differing in Nb, C, and N content, Nb/(C + N) factor, P + S content, and base metal ferrite content. A combination of Gleeble hot ductility and spot varestraint tests, followed by optical and electron metallography, was employed to elucidate the role of Nb in such persistent cracking. Susceptibility to HAZ cracking as a result of liquation was always found to be associated with eutectics of Nb rich phases and austenite, but with a complex interplay between the Nb/(C + N) factor, the P + S impurity level, Nb carbide or carbonitride size and distribution, ferrite number, and ferrite form and distribution in the base metal. A key role for composition and also base metal thermomechanical processing is suggested that merits more intensive systematic study.

Mathematical modeling of the extrusion of 6061/Al2O3/20p composite

An integrated approach, involving laboratory experiments, extrusion plant trials, and finite element modeling (FEM) has been adopted for the study of the extrusion of the metal matrix composite (MMC) 6061/Al2O3/20p. Gleeble compression tests were performed to develop the constitutive equation of the MMC under industrial extrusion process conditions. Extrusion plant trials were conducted to measure load and temperature and to obtain samples for microstructural analysis. Metal flow, with respect to particle behavior in the deformation zone, was examined microscopically. An FEM based on the commercial code DEFORM was adopted for the simulation of the extrusion of the MMC; the constitutive equation developed was incorporated into the model. Using an updated Lagrangian formulation, both the transient and steady-state regions of extrusion were modeled. Load and temperature predictions resulting from this model agree well with the measured values in the upsetting stage and in the steady-state region. Temperature predictions agree to within less than 3 pct of the measured values. The FEM predictions of temperature, stress, strain, and strain-rate distribution were correlated with the particle behavior and low-speed cracking during extrusion: large shear deformation promotes particle fracture in the deformation zone, and tensile stress generation in the die land zone of the billet leads to low-speed cracking of the MMC during extrusion. The latter occurs at low temperature in the front end of the billet at the beginning of the extrusion process due to heat loss to the cold die.

Modeling microstructural development during the forging of Waspaloy

A model for predicting the evolution of microstructure in Waspaloy during thermomechanical proc-essing was developed in terms of dynamic recrystallization (DRX), metadynamic recrystallization, and grain growth phenomena. Three sets of experiments were conducted to develop the model: (1) preheating tests to model grain growth prior to hot deformation; (2) compression tests in a Gleeble testing machine with different deformation and cooling conditions to model DRX, metadynamic recrystallization, and short time grain growth during the post deformation dwell period and cooling; and (3) pancake and closed die forging tests conducted in a manufacturing environment to verify and refine the model. The microstructural model was combined with finite element modeling (FEM) to predict microstructure development during forging of Waspaloy. Model predictions showed good agreement with microstructures obtained in actual isothermal and hammer forgings carried out at a forging shop.

Solidification morphology and semi-solid deformation in superalloy Rene 108

A high temperature nickel-base superalloy (Rene 108) was directionally solidified by imposing various growth rates and thermal gradients using a modified Bridgeman apparatus. The scaling of the solidification structure was recorded as a function of the imposed growth variables. A special Gleeble testing procedure, developed previously where the solidified samples were quickly raised to a predetermined temperature in the semi-solid zone and fractured, was used for the measurement of fracture conditions in the semi-solid region. The effect of the solidification process variables, namely, the temperature gradient and velocity, on the fracture stress in the transverse direction was to increase the fracture stress at a given temperature. The upper hot-tearing temperature was noted to be a function of the solidification variables. The amount of strain accommodation and the hot tearing resistance was found to be influenced by the solidification microstructure. Fracture maps, which include the temperature, transverse fracture stress and temperature gradient during solidification (T-σT-G), for the directionally solidified microstructures are presented. Castability maps are created from the microstructure and the fracture data and display the porosity and semi-solid strength as a function of the casting variables.

Solidification morphology and semisolid deformation in the superalloy Rene 108

A high-temperature nickel-base superalloy (Rene 108) was solidified at various cooling rates. The morphology of the equiaxed microstructure and the mechanism for intrinsic microporosity formation were correlated to the processing parameters. A special Gleeble testing procedure (developed previously — where the samples were quickly raised to a predetermined temperature in the semisolid zone and fractured) was used for the measurement of the fracture data. The upper coherent temperature was noted to be a function of the solidification variables. The amount of strain accommodation and the hot-tearing resistance was found to be influenced by the solidification microstructure. The hot ductility, the semisolid strength, and the corresponding microstructural changes are examined and discussed. Fracture maps which include the temperature, transverse-fracture stress and cooling rate during solidification $$(T - \sigma _T - \dot T)$$ for the equiaxed solidified microstructures are presented. A castability map was created from the fracture data.

A study on the formation of liquation cracks in the weld heat-affected zone of HY-80 quenched and tempered steel

Liquation cracking of heat-affected zones (HAZs) is often encountered during the welding of HY-80 steels. To reduce the sensitivity of this defect, the content of impurities, such as P and S, must be kept as low as possible. However, in the development of HY-80 steel, HAZ grain boundary liquation is still found even at very low impurity contents. In order to clarify the cause of this defect, the Gleeble hot ductility test and electron probe X-ray microanalysis (EPMA) were carried out. From the results of EPMA, it was evident that the grain boundary liquation in the heat-affected zone of HY-80 steel was due to the low-melting-point eutectic reaction between Cr, Ni and Mn, which had been swept up by the migrating grain boundaries in the welding-heating thermal cycle, and hence enriched at the grain boundary. In addition, the Gleeble hot ductility test results revealed that the HAZ liquation cracking sensitivity of HY-80 steel could be decreased by reducing the C, Ni and Cr contents of base metal, and by decreasing the dwell time at high temperatures during the welding thermal cycle.

Effect of Minor Alloying Elements on Hot-Workability of Ni-Cr-W Superalloys.

Research and development have been carried out on new heavy duty Ni-Cr-W superalloys for application to the structural components of high-temperature gas-cooled reactors with coolant outlet temperatures of around 1,000°C. In the first step of the program, the basic chemical composition, i.e, Cr/W contents in the alloy was determined to be Ni-18 to 19 mass.% Cr-20 to 22 mass% W. In order to examine the effect of additional alloying elements, i.e, Si, Mn, Y, B, Ti etc, on the hot-workability, a series of high-strain-rate high-temperature tension tests, so-called Gleeble tests, was carried out on 21 heats of the alloys with the basic chemical composition of Ni-18 to 19 mass% Cr-20 to 22 mass% W. The addition of Si and Mn is extremely harmful to the hot-workability. On the contrary, the addition of Y is very effective in improving the hot-workability. The addition of B and Ti is also beneficial. Neither enrichment of C nor addition of Nb or Fe is significantly beneficial to the hot-workability. The multiple regression analysis technique is applicable to the prediction of the hot-workability of Ni-Cr-W superalloys.

Semi-solid deformation in multi-component nickel aluminide

A systematic study was carried out to determine the solidification and tensile behaviour of semi-solid multi-component nickel aluminide. Controlled equiaxed-solidified samples were tested at various temperatures in the mushy (semi-solid) region. A special Gleeble testing procedure was developed where the samples were quickly raised to a predetermined temperature in the semi-solid zone and fractured. The fracture stress was noted to decrease monotonically with temperature. The strain to fracture exhibited a ductility minimum at an intermediate temperature in the semi-solid zone. For the equiaxed-solidified samples, the fracture stress was found to decrease with increasing cooling rate at any given temperature

Semi-solid deformation in multi-component nickel aluminide

A systematic study was carried out to determine the solidification and the tensile behaviour of semi-solid multicomponent nickel aluminide. Directionally solidified samples were tested at various temperatures in the mushy (semi-solid) region. A special Gleeble testing procedure was developed where transverse and longitudinal (5 mm) samples were quickly raised to a predetermined temperature in the semi-solid zone and fractured. The fracture stresses were found to decrease monotonically with temperature. The strain to fracture exhibited a ductility minimum at an intermediate temperature in the semi-solid zone. The effect of the solidification process variables, namely, the temperature gradient and velocity, on the fracture stress in the transverse direction was to increase the fracture stress at a given temperature. In the longitudinal direction, the fracture stress decreases with the temperature gradient and was relatively independent of velocity. At the temperature corresponding to the strain minimum, residual microcracks were detected on the fracture surface. The upper hot tearing temperature was noted to be a function of the solidification variables. The amount of strain accommodation and the hot tearing resistance was found to be influenced by the solidification microstructure. Fracture maps which include the transverse fracture stress, temperature, and temperature gradient during solidification (σT-T-G) for the directionally solidified microstructures are presented. A castability map is created from the fracture data.

Transverse cracking in continuously cast HSLA slabs – influence of composition

Transverse cracking in continuously cast microalloyed and low-alloyed steels has been shown to occur by a mechanism involving the formation of cavities at grain boundaries. Cavities are nucleated primarily at MnS and AIN particles. Crack formation by this mechanism can be minimized by encouraging stress relaxation away from grain boundaries and by avoiding the precipitation of sulphide and nitride particles on the grain boundaries. Gleeble testing has shown that the hot strength may be reduced and, therefore, the degree of stress relaxation improved, by minimizing alloying addition, particularly of Nb, V, and N in microalloyed steels and Cr, Ni, and Mo in low-alloy steels. Precipitation on grain boundaries may be reduced by additions of Ca and/or Ce or Ti and/or Zr, which cause the sulphides and nitrides, respectively, to precipitate in the liquid. Temperature cycling, particularly through the α–γ transformation, should also be avoided. The use of such measures has resulted in the production of C–Mn–Nb–Al slabs, > 300 mm thick, which do not require any surface dressing before rolling.MST/51

Transverse cracking in continuously cast HSLA slabs – influence of composition

Transverse cracking in continuously cast microalloyed and low-alloyed steels has been shown to occur by a mechanism involving the formation of cavities at grain boundaries. Cavities are nucleated primarily at MnS and AIN particles. Crack formation by this mechanism can be minimized by encouraging stress relaxation away from grain boundaries and by avoiding the precipitation of sulphide and nitride particles on the grain boundaries. Gleeble testing has shown that the hot strength may be reduced and, therefore, the degree of stress relaxation improved, by minimizing alloying addition, particularly of Nb, V, and N in microalloyed steels and Cr, Ni, and Mo in low-alloy steels. Precipitation on grain boundaries may be reduced by additions of Ca and/or Ce or Ti and/or Zr, which cause the sulphides and nitrides, respectively, to precipitate in the liquid. Temperature cycling, particularly through the α–γ transformation, should also be avoided. The use of such measures has resulted in the production of C–Mn–Nb–Al slabs, > 300 mm thick, which do not require any surface dressing before rolling.MST/51

The effect of minor elements on the hot-workability of nickel-based superalloys

We have investigated the effect of five minor elements, S, Ca, Mg, Y and Zr, on the hotworkability of three solid solution strengthened nickel-based superalloys, Inconel 600, Hastelloy-X and a Ni-Cr-W type prospective alloy (NSC-1) for heat exchanger pipes in high temperature gas reactors. The hot-workability was evaluated from the reduction in area of hot tensile specimens by using a Gleeble testing machine. Round bar specimens were prepared from the near-surface portion of the alloy ingots, melted and cast by vacuum induction melting, vacuum arc remelting or electro-slag remelting. When the S content increases, a ductility dip appears between 1050 and 1150 °C on each alloy; the greater the S content, the deeper the dip. At the same time, the fracture appearance becomes more and more intergranular. By adding a small amount of Ca, Mg, Y or Zr, the hot-workability of the alloys changed drastically, and it was found that a controlled addition of these minor elements gave a superior hot ductility

非水溶媒系電解液定電位電解エッチング法による鋼中のリン化物の観察と分析

Phosphides in carbon steel and stainless steel are studied using the non-aqueous electrolytepotentiostatic etching method. The results are summarized as follows.(1) Niobium phosphide is found in austenitic stainless steel (SUS 347). The phosphide is fine and eutectic and located in fracture surface of the steel strained at high temperature by Gleeble Test Device. According to the X-ray diffraction analysis of the residues extracted from the steel, the phosphide is identified as Nb8P5 (orthorhombic: a0=2.62 nm, b0=0.947 nm, c=0.346 nm).(2) Titanium phosphides are found in continuously cast slab of ferritic stainless steel (SUS 430). The phosphides are needle-, plate-like and dendritic. From the X-ray diffraction analysis of the phosphides, Ti3P(Cr3PN type, orthorhombic), Ti4P3(cubic) and TiP(hexagonal) are found.(3) Titanium phosphide is found in carbon steel (0.014%P-0.16%Ti). The phosphide is identified as Ti∼1.7P(orthorhombic) by X-ray diffraction analysis of the extracted residues. Ti/P ratio of the residues is about 1.2. The phosphide precipitates above 873 K and the maximum of the precipitation is found in the temperature range from 973 to 1073 K.

Hot-ductility behaviour of C–Mn–Nb–Al steels and its relationship to crack propagation during the straightening of continuously cast strand

The influence of composition on the tendency for surface-crack propagation to occur on straightening of continuously cast strand of a commercial C–Mn–Nb–Al grade of steel has been examined and compared with the hot-ductility behaviour obtained from Gleeble tensile tests, using reduction of area as the measure for hot ductility. The tendency for surface-crack propagation was found to increase with Nb and soluble Al addition and to decrease with a rise in the P level. Hot ductility was also found to be affected in a similar manner by these elements. The results have been interpreted in terms of differences in the effectiveness of the NbCN precipitation in pinning the γ grain boundaries during deformation. From the close agreement between the hot-ductility behaviour as given by the Gleeble tests and the tendency for surface cracks to propagate during straightening of these steels at the exit from the continuous-casting machine, it has been concluded that the Gleeble test can be used with a fair degree of confidence to predict the behaviour on straightening of other steel compositions made by the continuous-casting process.

Effect of minor elements on hot workability of nickel-base superalloys

AbstractStudies have been performed on the effect of five minor elements (S, Ca, Mg, Y, and Zr) on the hot workability of three solid-solution strengthened, nickel-base superalloys: Inconel 600, Hastelloy-X, and a Ni–Cr–W type alloy (NSC-1) for heat-exchanger pipes in high-temperature gas reactors. The hot workability was evaluated from the reduction of area in hot tensile tests using a Gleeble testing machine. Round bar specimens were prepared from near surface portions of alloy ingots melted and cast by vacuum induction melting, vacuum arc remelting, or electroslag remelting. When the sulphur content was increased, a ductility dip appeared for each alloy between 950° and 1150°C; the greater the sulphur content, the deeper the dip. At the same time, the fracture appearance became increasingly intergranular. By adding a small amount of Ca, Mg, Y, or Zr, the hot workability of these alloys changed drastically, and it was found that controlled addition of these minor elements gave a superior hot ductility. ...