Mechanical properties of AISI 1045 ceramic coated materials by nano indentation and crack opening displacement method

WANG Yan-rong(王燕荣), WANG Yi-qi(王一奇), HUI Zhi-peng(惠志鹏), SONG Jung-il

(Department of Mechanical Engineering, Changwon National University, Changwon 641-773, Korea)

Abstract:An effective approach was conducted for estimating fracture toughness using the crack opening displacement (COD) method for plasma enhanced chemical vapor deposition (PECVD) coating materials. For this evaluation, an elastoplastic analysis was used to estimate critical COD values for single edge notched bending (SENB) specimens. The relationship between fracture toughness (K_IC) and critical COD for SENB specimens was obtained. Microstructure of the interface between Al₂O₃-TiO₂ composite ceramic coatings and AISI 1045 steel substrates was studied by using scanning electron microscope (SEM). Chemical compositions were clarified by energy-dispersive X-ray spectroscopy (EDS). The results show that the interface between of Al₂O₃-TiO₂ and substrate has mechanical combining. The nanohardness of the coatings can reach 1 200 GPa examined by nanoindentation. The K_IC was calculated according to this relationship from critical COD. The bending process produces a significant relationship of COD independent of the axial force applied. Fractographic analysis was conducted to determine the crack length. From the physical analysis of nanoindentation curves, the elastic modulus of 1045/Al₂O₃-TiO₂ is 180 GPa for the 50 μm film. The highest value of fracture toughness for 1045/Al₂O₃-TiO₂-250 μm is 348 MPa·m^l/2.

Key words:crack opening displacement (COD); single edge notched bending (SENB); plasma enhanced chemical vapor deposition (PECVD); fracture toughness; nanoindentation