Nickel-base Superalloy Welding S. A. David & S. S. Babu Metals and Ceramics Division Oak Ridge National Laboratory Oak Ridge, TN 37831-6096 Departmental Seminar Outline Background Experimental Alloys Weld Cracking Monitoring of weld cracks Welding Process Parameters on Weld Cracking
S. A. David & S. S. Babu
Metals and Ceramics Division
Oak Ridge National LaboratoryOak Ridge, TN 37831-6096
Significant breakthroughs have taken place in alloy design and processing of nickel based superalloys to meet the demands on turbine airfoils which operate at high temperatures.
air craft engine blade
land based turbine engine blades
(small amounts of Mo and Re)
Welding Speed: 12.6 mm/s
Welding Speed: 16.8 mm/s
Welding Speed: 25.2 mm/s
Using a geometric analysis and expressing the solidification front normal and the crystallographic growth directions in terms of a fixed set of reference axes, dendrite growth selection process can be calculated.
(001) Surface -  Weld
CrCrCrCrReReReRe...Ni...NiCrCrCrNiNiNiNiNiNiNiNiAlAlNiNiNiNiNi....TaAPFIM Data Analysis
low-speed laser welds
50 nmIn certain cases, the conventional microstructural development can be drastically altered. For example CMSX-4 pulsed laser welds.
Feng, et. al. 1996
Uncoupled Finite Element Model
100 °C / s
10 °C / s
In this work, the phase transformations and microstructure development were investigated under controlled cooling conditions.
Ni - 5.5% Al - 8.0% Cr - 0.8% Ti - 9.0% Co - 3.2% Ta - 9.5% W (wt.%)
0.17 °C/sMicrostructure development during slow cooling was similar to that of base metal microstructure.
Number density of ´ precipitates increased with an increase in cooling rate from 1300°C.
Chromium atom image obtained from atom probe tomography revealed both g matrix and g´ precipitates.
Interconnected g´ and distinct g´ precipitates were observed based on 15 at.% Cr surfaces.
Atom probe tomography from samples cooled at 75 °C/s failed to show any interconnected g´ precipitate morphology
Thermodynamic calculations allow us to predict the formation of g´precipitates.
Diffusion controlled growth calculations predict the kinetics of g´ formation during cooling at 500°C/s from 1300°C.
Simulated concentration profiles are compared with the measured APFIM concentration profiles.
Experimental and modeling results are necessary to design welding process parameters and post weld heat treatment conditions.