A STUDY OF FRICTION-INDUCED MARTENSITIC-TRANSFORMATION FOR AUSTENITICMANGANESE STEEL

The microstructural changes in worn surfaces of Mn6 and Mn13 steels be fore and after wear were investigated by the use of SEM, TEM and a bac k-scatter Mossbauer spectrometer. The results show that there exist tw o kinds of austenite for austenitic manganese steels before wear, one contains almost no carbon (C) and the other contains more C. The C ato ms mainly exist in the octahedral interstitial sites of austenite. The re is only one C atom as nearest neighbour around an iron atom. Corres pondingly two kinds of friction-induced martensite are produced in the worn surface of the Mn6 steel during wear. One is C-and metallic allo ying element (Mn)-free martensite whose internal magnetic field value equals 33.0 T and the other is C-and Mn-containing martensite whose in ternal magnetic field value equals 30.7 T. The C-and Mn-free martensit e is produced under low wear impact energy firstly and its fraction re aches a saturated value rapidly. However, the C-and Mn-containing mart ensite is produced under high wear impact energy and its fraction incr eases with increasing impact energy of the wear test. No friction-indu ced martensitic transformation in the Mn13 steel exists during wear. T he friction-induced martensite mainly nucleates at the stress concentr ation caused by plastic deformation such as the austenite grain bounda ries and slip bands in the Mn6 steel. (C) 1997 Elsevier Science S.A.