Proceedings of SerbiaTrib '13

Serbian TribologySocietySERBIATRIB ‘1313 th International Conference onTribologyKragujevac, Serbia, 15 – 17 May 2013Faculty of Engineeringin KragujevacWEAR BEHAVIOR OF AUSTEMPERED DUCTILE IRONWITH NANOSIZED ADDITIVESJ. KaleichevaTechnical University of Sofia, Bulgaria, e-mail: jkaleich@tu-sofia.bgAbstract: The microstructure and properties of austempered ductile iron (ADI) strengthened withnanosized addtives of titanium nitride + titanium carbonitride (TiN + TiCN), titanium nitride TiN and cubicboron nitride cBN are investigated. The TiN, TiCN and cBN, nanosized particles are coated by electrolessnickel coating EFTTOM-NICKEL prior to the edition to the melt. The spheroidal graphite iron samples areundergoing an austempering, including heating at 900 о С for an hour, after that isothermal retention at 280о С, 2 h and 380 о С, 2h. The metallographic analysis by optical metallographic microscope GX41 OLIMPUSand hardness measurements by Vickers Method are performed. The structure of the austempered ductileiron consists of lower bainite and upper bainite.Experimental investigation of the wear by fixed abrasiveare also carried out. The influence of the nanosized additives on the microstructure, mechanical andtribological properties of the austempered ductile irons (ADI) is studied.Keywords: nanosized particles, austempered ductile iron, hardness, wear resistance1. INTRODUCTIONThe austempering of the iron-carbon alloys is anisothermal heat treatment, which reduces theinternal stresses and deformations and increases thedetails’ impact strength. The bainitic structure isformed at this type of heat treatment, which iswidely applicable in constructional steels andductile iron processing due to its high strength andincreased toughness [1-2]. Incompleteaustempering is also applied in case of heattreatment of some hypereutectoid and ledeburitesteels [3]. The possibility of wider practicalapplication of this heat treatment type requires anadditional data for the bainitic transformation iniron-carbon alloys with different compositionincluding alloys with nanomodifiers. Nanosizedparticles added to the iron melt in a small quantitytransform the graphite morphology from laminar tovermicular one [5], increase the graphite quantity[6] and change the matrix structure, whichincreases the cast iron wear resistance [4-6].The aim of the performed investigation is tostudy the tribological properties, the microstructureand hardness of austempered ductile iron,containing additives of nanosized particles –titanium nitride+titanium carbonitride (TiN +TiCN), titanium nitride TiN and cubic boron nitridecBN.2. MATERIAL AND INVESTIGATIONMETHODSThe composition of the austempered cast ironsamples is: Fe-3,55C-2,67Si-0,31Mn-0,009S-0,027P-0,040Cu-0,025Cr-0,08Ni-0,06Mg wt%. TheTiN, TiCN and cBN, nanosized particles are coatedby electroless nickel coating EFTTOM-NICKEL[7] prior to the edition to the melt. The nickelcoating improves the particles wetting into the meltand their uniformity distribution into the castingvolume.The ductile cast iron samples are undergoingaustempering, including heat treatment at 900 о С foran hour, after that isothermal retention at 280 о С, 2h and 380 о С, 2h.The austempered ductile iron samples’microstructure is observed by means of an opticalmetallographic microscope GX41 OLIMPUS. Thesamples surface is treated with 2 % HNO3 -C2H5OH solution. The hardness testing isperformed by Vickers method (Table 1).The experimental wear examination of the castand austempered ductile iron (ADI) is performed in13 th International Conference on Tribology – Serbiatrib’13 37