Considering the propensity for iron carbon reactions

Fig. 11(c) presents a low magnification scanning Tanespimycin micrograph of an NSD deposition onto a borided 440C ball bearing in order to gauge overall adherence of the NSD film. The image is divided into areas of light and dark gray. The former correspond to areas of adhered film, and the dark regions are where the film has either delaminated or not fully coalesced. Fig. 9(d) displays a higher magnification image in a region where the NSD coating either delaminated or did not fully coalesce. Many roughly spherical-shaped particles of varying in size are present. These are likely intermediate phases of chromium carbides convergent plate boundary nucleate at the initial stage of the NSD deposition. Of critical importance is the tubular features observed within the image. These are most likely carbon nanotubes that often nucleate from transition metals such as iron. They pose a significant problem to NSD film adhesion and are therefore undesirable. They indicate the presence of elemental iron at the bearing surface in sufficient concentration to promote the formation of sp2 bonded carbon.