Nickel-based super alloy microstructure characterization of EBSD

Figure 1: the use of the ARGUS imaging detector phase contrast figure, according to at least four different phase.There are many small at the phase boundaries precipitates.EBSD/EDS synchronous measurement results as shown in figure 2 and figure 5.

Nickel-based super alloy because of its excellent mechanical strength, thermal creep deformation, fatigue resistance, corrosion resistance, or oxidation is known.As a result, they are often used in gas turbine and aeroengine of choice for high temperature structural materials.Characterization of the microstructure features for the control of mechanical properties is crucial.In addition, from the second phase precipitates (ɣ ', nitrite, carbide) solid solution and precipitation facies is the key to realize the high temperature strength;Therefore, strengthening the unknown precipitates formed in the process of characterization is critical.

In the application example, we reveal the EDS auxiliary EBSD measurements at different stages (including fine sediment) the importance of successful identification and calibration.Measure area in figure 1 of the phase contrast is visible on the map (using the ARGUS ™ BSE detector).Can be inferred from the ARGUS image many fine precipitates (carbide) and other three different phase.Combining with the EBSD/EDS measurements, the spatial resolution of 50 nm small step.EBSD results as shown in figure 2, 5 and 6.Using EDS and EBSD synchronous measurement method to determine the four phase: nickel (substrate) and nickel aluminum, nickel, tungsten, and tantalum carbide.

The challenge of the test is successfully differentiate carbide and nickel matrix.Both with cubic FCC structure, so can produce very similar to the diffraction pattern (see figure 3 and 4).To this end, EDS auxiliary EBSD offline calibration corrected data.The result is shown in figure 5.

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Figure 2: untreated EBSD phase diagram.Possessions are using EDS and EBSD combination test.Nickel base, according to the phase in red leicester and displayed in blue, TaNiC shows as yellow, NiW display for the green.The calibration rate is 97%.EBSD cannot easily distinguish between carbide and nickel phase, because they have similar lattice parameters, lead to similar diffraction patterns (see figure 3 and figure 4).Therefore, in the process of EBSD calibration need help EDS.Because of EDS and EBSD synchronous measurement, so without SEM offline correction phase data.

Figure 3: the crystallography of nickel-based phase information, cubic FCC structure, with a cell and the corresponding spherical kikuchi patterns (kinematics simulation).

Figure 4: nickel tantalum carbide phase information of crystallography, cubic NaCl structure, with a cell and the corresponding spherical kikuchi patterns (kinematics simulation).

Figure 5: the EDS auxiliary EBSD phase diagram: possessions with the help of EDS is divided.Calibration rate was 98.6%, the correct standard, fine carbide identify properly solved.EDS auxiliary EBSD measure calibration can be online or offline in SEM, allows correction of phase measurement at any time, without having to spend extra on SEM test time.