Microstructure and mechanical properties of Fe matrix composites reinforced by nickel-chromium double-layer coated ZTAP ceramics

The preparation, microstructure and mechanical properties of ZTA particles reinforced Fe matrix composites (ZTA(P)/Fe composites) were systematically investigated. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) were used to analyze the microstructure and phase constituents, the hardness (H), Young's modulus (E) and plasticity factor (delta(A)) were determined as well. The nickel-chromium double-layer coated ZTA(P) of core-shell structure was prepared by electroless plating and multi-arc ion plating technologies. The modified ZTA(P) is consisted of the alpha-Al2O3, t-ZrO2, alpha-Cr and gamma-Ni phases. In addition, the compressive strength of ceramic preforms is high due to a compact sintering neck formed among ZTA(P) during high temperature sintering. The preferred sintering process for ZTA ceramic preforms is determined as 1350 degrees C + 1 h, in this case the preforms show the remarkable porosity and highest compressive strength which are 27.8% and 35.0 MPa, respectively. The interfacial metallurgical chemical reactions occurred during infiltration casting process, which ensure the excellent metallurgical interfacial bonding of the ZTA(P)/Fe composites. The interface contains double transition layers, which refer to silicate and CrFe phases, respectively. The H, E and delta(A) of interfacial double transition layers were measured by the nano-indentation method, the values of which are situated between the ZTA(P) and iron matrix.