Microstructural changes on the surfaces of a number of railway lines in ser
vice for a number of years were investigated using optical light microscopy
, micro-hardness measurements and TEM. Unequivocally areas were identified
containing so-called "white etching layers", the hardness of which was almo
st twice that of the pearlitic parent steel. The TEM investigations indicat
ed that the pearlite colonies had been dissolved just beneath the surface o
f the rails as a result of very heavy plastic deformation, forming a nano-c
rystalline microstructure of ferrite containing small amounts of cementite.
In one case signs of a partial transformation of the nano-crystalline micr
ostructure to martensite were observed.