Combined electron-ion-plasma treatment of 40Cr steel surface

Complex alloying, combining in a certain sequence the saturation of surface layer of material with atoms of metals and gases, is now widely used in most industrialized countries of the world. The present work is devoted to the revelation and analysis of dependences of element and phase composition, defect substructure, mechanical (microhardness) and tribological (wear resistance and friction coefficient) properties changes of alloying carbon steel subjected to combined treatment including the saturation of the sample surface layer by aluminum and subsequent nitriding. The material used for the study was AISI 5135 steel, which in the initial state has a structure represented by ferrite grains and pearlite grains of lamellar morphology. The combined modification was carried out in a single vacuum space on the TRIO setup with the chamber dimensions of 600×600×600 mm3 equipped by switching unit for realization of elion (electron and ion) mode of treatment. Aluminizing was carried out at the temperature of 963 К during 4 h. The cathode of electroarc evaporator was made of A7 grade aluminum alloy (98.8 % Al). Subsequent nitriding of aluminized layer was carried out at the temperature of 803 К during 2 h. It was established that the modified layer with the thickness of 70 μm is formed as a result of the combined treatment. It is demonstrated that the combined steel modification is accompanied by the formation of multiphase submicro- and nanostructure state including aluminum nitrides, iron and chromium nitrides and aluminides. It is revealed that the steel hardness is maximal on the modification surface and it exceeds by 3 times that of the initial steel. Wear resistance under the dry conditions decreases after the combined modification.