Abstracts Book - IMRC 2018

• SD7-P011
EFFECT OF CHROMIUM AS GRAIN GROWTH INHIBITOR IN WC-
10CO ALLOYS
Carlos Gamaliel Garay Reyes 1 , Marco Antonio Ruiz Esparza Rodriguez 1 , Ivanovich Estrada 1 ,
Sergio Eliseo Hernández Martínez 2 , Jose Luis Hernandez Rivera 2 , Jose de Jesus Cruz Rivera 2 ,
Javier Servando Castro 3 , Roberto Martinez Sanchez 1
1 Centro de Investigación en Materiales Avanzados, S.C., Metalurgia e Integridad Estructural,
Mexico. 2 Universidad Autónoma de San Luis Potosí, Instituto de Metalurgia, Mexico.
3 Universidad Autónoma de Ciudad Juárez, Facultad de Ingenieria, Mexico.
Applications of WC-Co alloys include all areas where conventional materials are
used. The nanostructured systems are preferred because the useful life of the
tooling increasing by reduction in grain size of WC phase. Conventionally, WC–
Co alloys are fabricated by mixing, compaction and sintering. The liquid-phase
sintering is carried-out above eutectic temperature of WC–Co. In the case of WC
phase the grain growth is favored by high interfacial free energy. For this reason,
the addition of grain growth inhibitors is necessary to control this growth during
sintering either by modifying the WC-Co interface or by providing diffusion
resistance. The starting materials consist of commercial WC and elemental
powders of Co and Cr (99.95% pure). The nominal compositions of mixture were
WC-10Co and WC-10Co(1Cr). Nanostructured powders were synthetized by
milling process (high energy mill). The milled mixtures were consolidated by HIP
at 1200 and 1350°C. The structural and microstructure characterization and
phases evolution was performed by XRD, SEM and Vickers hardness.
Estimations of the crystal sizes were calculated by the Scherrer equation and the
density measurements were determined by the Archimedes method. The
results show that crystallite size of WC phase in the WC-10Co and WC-10Co(1Cr)
samples after sintering at 1200°C, present an increase of 121.7 and 24.7% in its
value, respect to milled mixtures. For the WC-10Co(1Cr) samples after sintering
at 1350°C present an increase of 56%. The microstructure of WC-10Co(1Cr)
sample sintering at 1200°C show a bimodal particle size distribution attributed
to the Cr effect as particle growth inhibitor, which may be due to decrease in
growth rate during re-precipitation. The higher values of density and Vickers
microhardness are obtained in the WC-10Co(1Cr) sample after sintering at
1350°C, which is attributed to a high degree packing density and the effect of Cr
as grain growth inhibitor.
Keywords: Grain growth inhibitor, WC-10Co alloys, Chromium
Presenting authors email: roberto.martinez@cimav.edu.mx