iTSSe TSS A D V A N C E D M A T E R I A L S & P R O C E S S E S | A P R I L 2 0 2 2 3 9 iTSSe TSS A nanoindentation test is usually performed as a depth-sensing indentation test using a diamond Berkovich indenter with a nominal edge radius of 100 nm. Hardness and elastic modulus are measured at loads ranging between 1 and 500 mN, at a loading/unloading rate of 200 μN/s. Data are analyzed using the Oliver-Pharr method. Figure 3a shows an example of the hardness-versus-displacement curve. Figure 3b shows a modulus displacement curve after a series of nanoindentation tests were made on a Cu-10wt%Zn cold spray coating. Nanoindentation testing is a valuable tool to characterize the extent of plastic deformation and recovery in cold spray coatings. Figure 3c is a plot of the nanohardness of a copper-nickel composite coating that makes it possible to distinguish the relative fractions. Figure 3d is an image quality map taken using electron backscatter diffraction (EBSD), combined with corresponding nanohardness, to help deduce that static recrystallization takes place in cold sprayed copper. The sample surface must be absolutely flat and polished prior to carrying out nanoindentation tests. ~iTSSe For more information: This article series is adapted from Chapter 5, Cold Spray—Advanced Characterization authored by Dheepa Srinivasan in “High Pressure Cold Spray—Principles and Applications,” edited by Charles M. Kay and J. Karthikeyan (ASM, 2016). Complete references are included in this volume. The author may be reached at dheepasrinivasan6@gmail.com. Fig. 3 — Nanoindentation of cryomilled Cu-10Zn cold spray coating showing (a) hardness and (b) modulus of elasticity; (c) nanohardness of as-sprayed copper and nickel coatings, with hardness (superimposed red line) of the feedstock powders; and (d) EBSD characterization of the cross section of a nickel coating after nanoindentation. (a) (b) (c) (d) FEATURE 9
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