ELECTKON MICROSCOPY 





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(a) Normal illumination. (b) Phase-contrast showing nature of the surface 



Fig. 2. Stylus trace on an anodized aluminium surface. (After Scotti) lOOX 



edges of specimens and surface films from 

 damage during preparation for microscopic 

 and metallographic examination, and speci- 

 mens which have a non-conducting surface 

 may be successfully plated if a thin film of 

 metal is first deposited in a high vacuum. 

 For ease of manipulation specimens may be 

 mounted in a suitable plastic. 



Although much information can be derived 

 from the use of optical microscopy, as the 

 initiation of surface damage may be expected 

 to occur on a sub-microscopic scale a more 

 detailed surface examination is sometimes 

 required and the electron microscope can 

 be used to follow paths of exploration to 

 higher degrees of resolution (9). Examina- 

 tion may be made directly by reflection 

 (Halliday (10)) or by preparing surface 

 replicas which are examined in transmission. 

 The first method is limited to the use of 

 specimens sufficiently small to be accommo- 

 dated in the microscope, while the latter 

 method although occasionally subject to 

 artefacts has the advantage that the replica 

 may be taken from worn surfaces in situ 

 (Figs. 4 and 5). The transmission electron 

 microscope has successfully been used for 

 studying the initiation of wear and fretting 

 corrosion (4, 9). 



Fig. 3. Taper section of a worn surface showing 

 the surface contour, sub-surface metallographic 

 changes and indentations of a micro-hardness sur- 

 vey with V.P.N, superimposed. Etched Nital. 

 (After Scotti) 



H = 140X, V = 1400X 



careful use of metallurgical techniques of sec- 

 tioning, polishing and etching. It is essential 

 that the methods used do not change, obliter- 

 ate, or destroy in any way the evidence 

 being sought. Besides the conventional 

 methods, spark erosion machining (Nosov 

 and Bykov (7)) offers many advantages for 

 harder materials and specific applications 

 while electropolishing (Jacquet (8)) is use- 

 ful. Electroplating is used to protect the 



310 



