The effect of multiphase nitride inclusions on the surface roughness of 2083 plastic molds

The effect of multiphase nitride inclusion (MNIs) on the surface roughness of 2083 plastic molds was studied using surface analysis method, such as roughness measurement instrument, scanning field emission microscopy (SFEM) equipped with an energy dispersive X-ray spectrometry (EDX) and atomic force microscopy (AFM). The results of SEM and EDX analysis showed that the MNIs were combined of calcium aluminates core and TiN shell. During polishing, subsurface cracks was initiated at the interfaces between calcium aluminates core and TiN shell caused by the mismatch of the elastic modulus and thermal expansion coefficient, then, the cracks were propagated at the calcium aluminates core area due to stress concentration in the interface, led to separation of calcium aluminates core and formation of voids in the MNIs. Finally, the voids were connected to each other and resulted in the holes on the surface of the mold. Based on this work, it is suggested the surface roughness of 2083 plastic molds could be improved by reducing the concentration of the MNIs.