Comparison of surface and cross-sectional micro-nano mechanical properties of flame sprayed NiCrBSi coating

Nanoindentation was performed on both surface and cross-section of flame sprayed (FS) NiCrBSi coatings to compare the nano-scale mechanical properties of thermal spray coating in different directions. Conventional Vickers hardness measurement was carried out to measure the 'composite' properties and compare the possible discrepancies between the micro and the nano methods. Results indicate that at lower penetration depths indentation hardness (H-IT), indentation modulus (E-IT), and the ratio of elastic to total work of indentation (eta(IT)) depend on the intralamellar material properties and the values are higher, and H and E profiles come closest to coinciding in shape. At larger indentation depths the characteristics values and they reflect the 'composite' properties of coating units including splats, pores and cracks. H-IT and E-IT\ values of coating cross-section are superior to the surface. In all cases, the eta(IT) value of coating surface is higher than that of coating cross-section, probably due to more formations of intergranular and intersplat cracks during coating cross-sectional indentation which leads to more dissipation of the indentation energy. (C) 2016 Elsevier B.V. All rights reserved.