Surface Tension and Viscosity of the Ni-Based Superalloys LEK94 and CMSX-10 Measured by the Oscillating Drop Method on B
- PDF / 765,784 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 2 Downloads / 183 Views
DUCTION
NI-BASED superalloys are well established high-temperature materials. They are based on a two-phase mixture of the ordered and disordered intermetallic Ni3Al phases with additions of transition metals like Ti, Cr, Co; refractory elements like W, Mo, Ta; and elements of the Pt group like Re.[1,2] The typical Ni concentration is between 56 and 68 at. pct; Al concentration is between 8 and 16 at. pct; the refractory element concentration is between 3 and 8 at. pct; and Re concentration is in the range of 1 to 7 at. pct. The main application is for energy generation in land-based turbines and in the high-pressure section of jet engine turbines. One goal of current alloy development is an increase in the working temperature combined with high fatigue and creep resistance. The main production route is casting of turbine blades with directional single-crystalline solidification followed by extensive solution and annealing heat treatments to achieve the desired element distribution and microstructure. Optimization of production technology and of final product quality requires knowledge of the thermophysical properties in the high-temperature solid and in the liquid phase. Important thermophysical properties for a first-order casting simulation[3,4] are solidus and liquidus RAINER K. WUNDERLICH, Senior Research Scientist, and HANS-JO¨RG FECHT, Director, are with the Institute for Micro and Nanomaterials, Ulm University, Albert-Einstein-Alle 47,D-89081, Ulm, Germany. Contact e-mail: [email protected] GEORG LOHO¨FER, Senior Research Scientist, is with the Institut fu¨r Materialphysik im Weltraum, Deutsches Zentrum Luft- und Raumfahrt, DLR, Ko¨ln, Germany. Manuscript submitted January 29, 2016. Article published online November 9, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
temperatures, fraction solid-liquid, specific heat capacity, density, thermal conductivity, viscosity, and surface tension.[5] Knowledge of the surface tension and viscosity as a function of temperature are required for the modeling of surface and gravity driven flows, and together with the density and specific heat capacity as a function of temperature for the modeling of convective heat transfer. Other important issues are form filling in near net shape castings, and the prediction of defects such as bubble formation.[6] Due to their technical importance, continuous efforts are undertaken to measure thermophysical properties of Ni-based superalloys in the high-temperature solid[7,8] and in the liquid phase.[9–11] Because of the large variety of Ni-based superalloys, predictive models for the values of a variety of thermophysical properties have been developed.[12] The models require reliable input data at selected alloy compositions to allow for proper scaling over a larger concentration range. Measurements of thermophysical properties in the liquid phase at high temperatures with conventional thermoanalytic equipment are often complicated and fraught with error because of the presence of chemical or dissolution reactions between the liqui
Data Loading...
