Effect of Carbide Ceramic Zone on Wear Resistance of the (Fe,Cr)(7)C-3/Fe Surface Gradient Composite

摘要

In this work, we report on the influence of microstructure and mechanical properties of the (Fe,Cr)(7)C-3 ceramic zone on wear resistance of the (Fe,Cr)(7)C-3/Fe surface gradient composite fabricated by in situ synthesis method followed by a post-heat treatment at 1100 A degrees C for 20 h in argon atmosphere. The phase composition, microstructure, nanoindentation hardness, elastic modulus, fracture toughness, and relative wear resistance of the (Fe,Cr)(7)C-3/Fe surface gradient composite were investigated by means of x-ray diffraction, scanning electron microscopy, nanoindentation tester, and wear resistance testing instrument, respectively. The XRD results showed that (Fe,Cr)(7)C-3 is the predominant crystalline phases in the fabricated composite. The volume fraction of the (Fe,Cr)(7)C-3 particulates formed has a gradient distribution from the surface to the iron matrix, and the microstructure also changes significantly. The (Fe,Cr)(7)C-3 bulk ceramic zone with the volume fraction of about 100% and the (Fe,Cr)(7)C-3 dense ceramic zone with the volume fraction of about 90% were synthesized on the upper surface of the (Fe,Cr)(7)C-3/Fe surface gradient composite, respectively. The average nanoindentation hardness and elastic modulus of the (Fe,Cr)(7)C-3 bulk ceramic zone of the composite were determined to be 12.711 and 256.054 GPa, respectively. The fracture toughness of the (Fe,Cr)(7)C-3 bulk ceramic zone is in the range of 2.06-4.19 MPa m(1/2), and its relative wear resistance is about 56 times higher than that of the iron matrix. The (Fe,Cr)(7)C-3 dense ceramic zone with rod-like, secondary (Fe,Cr)(7)C-3 particulates was formed at the bottom of the (Fe,Cr)(7)C-3 bulk ceramic zone. Rod-like, secondary (Fe,Cr)(7)C-3 particulates are dense and grew in the direction of the iron substrate, providing higher wear resistance to the composite. The wear mechanisms of the (Fe,Cr)(7)C-3 bulk and dense ceramic zones are considered to be microcutting, microcracking, and spalling pit.