Designing spherical cementite in bainitic matrix (SCBM) microstructures in high carbon powder metal steels to improve dry sliding wear resistance

摘要

Spherical cementite particles in the bainitic matrix in high carbon steel processed by powder metallurgy (PM) method were produced and compared with separately sintered, fully bainitic and spherical cementite in the ferritic matrix microstructures for their microstructure-hardness-dry sliding wear properties. The primary cementite plus dense lamellar pearlite structures were achieved in the sintered specimens. The spherical cementites in the ferritic matrix (SCFM) were obtained by over-tempering of the martensite phase produced by quenching after the sintering process. To produce spherical cementite in the bainitic (SCBM) microstructure, SCFM specimens were partially austenitised at 735 degrees C over Ac-1 eutectoid temperature for 3 min and austempered at 300 degrees C for 1-2 h. Dry sliding wear resistance behavior of the specimens were examined under the constant load of 10 N at sliding distance of 1500 m. The dry sliding wear resistances of the SCBM specimens were much better than the microstructures produced by conventional heat treatments. (C) 2019 Elsevier B.V. All rights reserved.