Preparation of Cr-Mg-N-O Ceramics by Spark Plasma Sintering

Cr1−x-Mgx-N-O powders, with Mg content in metallic elements (x=Mg/Cr+Mg) ranging from 0 to 0.5, were synthesized from CrN and MgO powders using mechanical alloying under nitrogen atmosphere. Densification of these original powders is carried out by the spark plasma sintering is performed under a 70 MPa pressure and at 1200℃. The result of X-ray diffraction (XRD) indicated that (Cr, Mg)(N, O) phase with NaCl (B1) structure was synthesized in all the Cr-Mg-N-O powders. The MgO phase exists in the Cr-Mg-N-O ceramics for the higher Mg content of x=0.2, whereas the diffraction peaks attributed to MgO were not observed in the ceramics with x=0.1. The maximum Vickers hardness of HV 2050 was obtained for Cr1−x-Mgx-N-O ceramics with x=0.1, and was HV of approximately 500 higher than CrN ceramics (x=0). Moreover, the result of nano-indentation test showed that the Young's modulus of Cr1−x-Mgx-N-O ceramics increase from 398 GPa to 418 GPa in the x range 0 to 0.1.