Study of Thermo-Physical Properties of Selected Nickel-Based Superalloys With Use of DTA Method

2012 ◽  
Author(s):  
Jana Dobrovska ◽  
Simona Zla ◽  
Frantisek Kavicka ◽  
Bedrich Smetana ◽  
Vlastimil Vodarek
Keyword(s):  
Phase Transformation ◽  
Physical Properties ◽  
Phase Transformations ◽  
Solidus Temperature ◽  
Experimental System ◽  
Reaction Scheme ◽  
Transformation Temperatures ◽  
Heating And Cooling ◽  
Temperature Heating ◽  
Thermo Physical Properties

The presented paper deals with study of thermo-physical properties of cast complex alloyed nickel based superalloys IN713LC, IN738LC and IN792-5A. In this work the technique of Differential Thermal Analysis was selected for acquisition and comparison of the phase transformation temperatures. The samples taken from superalloys in as received state were analysed at heating and cooling rates of 1, 5, 10, and 20 K/min using the experimental system Setaram SETSYS 18TM. Moreover, the transformation temperatures for zero heating/cooling rate were calculated. Based on a comparison of these temperatures it is possible to make the following conclusions: (i) The alloy IN792-5A has the highest temperature of solubility of the strengthening phase γ′ (1235°C); (ii) the highest liquidus temperature (heating) obtained by extrapolation was found in the alloy IN713LC (1349°C), the lowest solidus temperature (heating) was found for the alloy IN738LC (1212°C); (iii) At cooling an undercooling occurred in all alloys. In general it may be stated that the biggest under-cooling (TS, 47°C) was recorded in the alloy IN792 5A; (iv) The width of the interval of the heat treatment window was the biggest in alloy IN713LC (44°C); (v) The alloy IN738LC is characterised by the widest interval of melting (124°C) and solidification (134°C), while the alloy IN792 5A has the narrowest interval of melting (82°C) and at the same time almost the same interval of solidification as the alloy IN738LC (129°C); (vi) The obtained phase transformation temperatures were compared with the values of phase transformations temperatures calculated on the basis of established relationships. In order to obtain more precise description of the behaviour of Ni-based superalloys, during controlled heating/cooling of the initial material (as received state) during DTA analyses, all the samples of superalloys were subjected to a phase analysis using scanning electron microscopy. The course of phase transformations, in all the studied superalloys (IN713LC, IN738LC, IN792 5A) is likely to run according to the following reaction scheme (L = melt): L ↔ γ, L ↔ γ + MC, L ↔ γ/γ′, L ↔ γ + minority phases (such as M3B2, phase η), γ ↔ γ′.

The DSC Investigation on Phase Transformations of Directionally Solidified (DS) and Powder Metallurgy (PM) Ni-Base Superalloys

2018 ◽  
Vol 941 ◽  
pp. 1035-1040
Author(s):  
Liang Zheng ◽  
Yu Feng Liu ◽  
Michael J. Gorley ◽  
Zu Liang Hong ◽  
Sarah Day ◽  
...  
Keyword(s):  
Particle Size ◽  
Phase Transformation ◽  
Powder Metallurgy ◽  
Phase Change ◽  
Phase Transformations ◽  
Cooling Rate ◽  
Cooling Curves ◽  
Directionally Solidified ◽  
Transformation Temperatures ◽  
Heating And Cooling

The phase transformations of the directionally solidified (DS) and powder metallurgy (PM) Ni-base superalloys were investigated by JMatPro, synchrotron XRD (SXRD) and differential scanning calorimetry (DSC). The minor phases, such as MC, eutectic γ′ and Ni5Hf, and γ matrix with secondary γ′ existed in as-cast microstructure of DS DZ22. However, only γ matrix was found in PM625 alloy powders. The phase change in both heating (melting) and cooling (solidification) process was investigated by DSC on DZ22 test bar and PM625 alloy powders respectively. The DSC experiment with different heating/cooling rates (5-40°C/min) was performed on DS superalloy DZ22. The results indicated that the heating/cooling rate had obvious effect on the DSC results of the phase transformation temperatures of liquidus, MC carbides, solidus, eutectic (γ+γ′) and secondary γ′. The heating and cooling DSC curves shifted to high and low temperature direction respectively, accompanied by the heating/cooling rate increased. However, the average values of specific peaks of heating and cooling curves are relatively consistent which is close to the equilibrium phase change temperatures of the alloy and makes the results comparable. Besides the average value method, the liquidus temperature of the alloy (0°C/min) can also be obtained by method of linear-fit/extrapolating from 5-40°C/min heating/cooling rates or inflection point deviate from the baseline of DSC cooling curves which could minimize the heating/cooling rate effects. The DSC experiment was carried out on PM625 superalloy powders with different particle size range (0-355μm), the results indicated that the particle size had minor effect on liquidus and solidus temperatures of DSC heating curves, the differences were less than 2°C. The change in phase transformation temperatures under different heating/cooling rate should be considered for selecting the process parameter (heat treatment, HIP or casting) for manufacturing Ni-base superalloy components.

Drug solid solutions – a method for tuning phase transformations

CrystEngComm ◽  
2014 ◽  
Vol 16 (26) ◽  
pp. 5827-5831 ◽  
Author(s):  
Amit Delori ◽  
Pauline Maclure ◽  
Rajni M. Bhardwaj ◽  
Andrea Johnston ◽  
Alastair J. Florence ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Solid Solutions ◽  
Transformation Temperatures

Tuning phase transformation temperatures through the use of solid solutions.

NUMERICAL MODELING OF PHASE TRANSFORMATION DURING GRINDING PROCESS

2017 ◽  
Vol 79 (5) ◽  
Author(s):  
Syed Mushtaq Ahmed Shah ◽  
M. A. Khattak ◽  
Muhammad Asad ◽  
Javed Iqbal ◽  
Saeed Badshah ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Thermal Stresses ◽  
Heating Temperature ◽  
Temperature History ◽  
Grinding Process ◽  
Cooling Rates ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Heating And Cooling

The rapid heating and cooling in a grinding process may cause phase transformations. This will introduce thermal strains and plastic strains simultaneously in a workpiece with substantial residual stresses. The properties of the workpiece material will change when phase transformation occurs. The extent of such change depends on the temperature history experienced and the instantaneous thermal stresses developed. To carry out a reliable residual stress analysis, a comprehensive modelling technique and a sophisticated computational procedure that can accommodate the property change with the metallurgical change of material need to be developed. The objective of this work is to propose a simplified model to predict phase evolution during given temperature history for heating and cooling as encountered during grinding process. The numerical implementation of the proposed model is carried out through the developed FORTRAN subroutine called PHASE using the FEM commercial software Abaqus®/standard. Micro-structural constituents are defined as state variables. They are computed and updated inside the subroutine PHASE. The heating temperature is assumed to be uniform while the cooling characteristics in relation to phase transformations are obtained from the continuous cooling transformation (CCT) diagram of the given material (here AISI 52100 steel). Four metallurgical phases are assumed for the simulations: austenite, pearlite, bainite, and martensite. It was shown that at low cooling rates high percentage of pearlite phase is obtained when the material is heated and cooled to ambient temperature. Bainite is formed usually at medium cooling rates. Similarly at high cooling rates maximum content of martensite may be observed. It is also shown that the continuous cooling transformation kinetics may be described by plotting the transformation temperature, directly against the cooling rate as an alternative to the continuous cooling transformation diagram. The simulated results are also compared with experimental results of Wever [20] and Hunkle [21] and are found to be in a very good agreement. The model may be used for further thermo-mechanical analysis coupled with phase transformation during grinding process.

CFD Investigation of Developing and Redeveloping Laminar Flow and Heat Transfer Characteristics in Coiled Tube Systems for Constant Wall Temperature Heating and Cooling: Part I — Toroid and Helical Configurations

2006 ◽  
Author(s):  
Anthony J. Bowman ◽  
Hyunjae Park
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Tube Radius ◽  
Coiled Tube ◽  
Cfd Models ◽  
Heating And Cooling ◽  
Flow And Heat Transfer ◽  
Temperature Heating ◽  
Thermo Physical Properties

In this paper developing laminar fluid flow and heat transfer performance in toroidal and helical coiled tube heat exchanger systems with coil-to-tube radius ratios (5 to 45) and small helical pitch are investigated using appropriate numerical modeling techniques available in the CFD package (Fluent v6.2). Base CFD models were primarily developed, optimized and compared with available published friction factor and heat transfer data and correlations for the toroidal and helical coil systems. With the proven CFD modeling technique and the results obtained, the analysis was extended to the coil-to-tube radius ratios of interest and to the investigation of the effect of thermo-physical properties of working fluids on the system thermal performance. The CFD models employ variable thermo-physical properties in the analysis of uniform wall temperature heating and cooling of common working fluids such as air and water. Defining appropriate dimensionless variables to describe the developing and redeveloping hydrodynamic and thermal flow for coiled tube systems, the variations of friction factor and local Nusselt number along the coil are investigated. It has been shown that in addition to the common affecting parameters, i.e. the coil-to-tube radius ratio and the Dean and Prandtl numbers, the heat transfer performance also depends upon the interactions (expansion and suppression) between the viscous and thermal boundary layers due to secondary flows caused by the centrifugal and torsional forces inherent in coiled tube systems. Upon investigation of the variations of the local dimensionless velocity and temperature along the coil length, it was found that for both heating and cooling conditions, fully-developed hydrodynamic and thermal conditions are not established in the coiled-tube system for the geometric constraints and system boundary and operating conditions used in this work. The case studies performed in this paper indicated approximately 20-30% higher for heating of water (20-30% lower for cooling of air and water) than values of heat transfer coefficients obtained from the reported correlations. The results obtained in this work can be used to correct/adjust the flow and thermal performance used in the design of toroidal and helical coiled tube systems.

scholarly journals Influence of Direct Thermal Analysis Experimental Conditions on Determination of the High Temperature Phase Transformation Temperatures / Wpływ Warunków Prowadzenia Bezpośredniej Analizy Termicznej Na Określenie Temperatur Wysoko Temperaturowych Przemian Fazowych

2015 ◽  
Vol 60 (4) ◽  
pp. 2867-2872
Author(s):  
K. Gryc ◽  
M. Strouhalová ◽  
B. Smetana ◽  
L. Socha ◽  
K. Michalek
Keyword(s):  
Thermal Analysis ◽  
Phase Transformation ◽  
Inert Atmosphere ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Laboratory System ◽  
Experimental Conditions ◽  
Standard Material ◽  
Transformation Temperatures ◽  
Heating And Cooling

Thermo-physical and thermodynamic properties of metallic systems represent some of the most important data that allows to describe their behaviour under strictly specified conditions. These data are the basic, input data for simulative programs, which can model this behaviour and they can be applied to real conditions. Method of direct thermal analysis is the one of the methods of enabling to obtain such data. This paper deals with application of this method on particular sample of pure standard material. The experimental laboratory system for thermal analysis Netzsch STA 449 F3 Jupiter was used for experimental measurements. This paper is studying the influence of experimental conditions on the obtained temperature of phase transformations and on shift of phase transformation temperatures with respect to the monitored experimental conditions, accuracy and credibility of the measured data. Acquired values of this data could be significantly influenced by experimental conditions, size (mass) of samples, purity of inert atmosphere and also by regimes of controlled heating and cooling rates.

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