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Zirconia-toughened alumina ceramic particle (ZTAP)-reinforced high Cr cast Fe matrix composites (ZTAP/Fe composites) are promising advanced wear-resistant materials. However, due to wear and tear, the ceramic particles may shed from the Fe matrix because of their low interfacial bonding properties. In the present work, we investigated interfacial characteristics and abrasive wear behaviours of ZTAP/Fe composites. Results showed that sintering played a significant role in the formation of sintering necks and consequently affected both compressive strengths and porosities of ZTA ceramic preforms. Optimum compressive strength (44.3 MPa) and porosity (25.2%) were obtained when sintering was performed at 1350 °C for 1 h. Subsequently, ZTAP/Fe composites without evident defects were fabricated by infiltration casting. Scanning electron microscopy, electron probe microanalysis and transmission electron microscopy were also used to analyse the microstructures and phase constituents of the interfacial layers of composites. Effects of applied wear loads on the wear behaviour evolutions and wear mechanisms of composites were examined. Wear resistances of ZTAP/Fe composites were found to be 1.64–2.21 times as compared to the Cr15 specimen. This work was funded by the National Natural Science Foundation of China (No. 51805408, 52175184), Guangxi Innovation Driven Development Project (GUIKEA A18242001), the Key-Area Research and Development Program of Guangdong Province (2019B010942001), and the Fundamental Research Funds for the Central Universities of China (xzy012019001, xtr0118008).

The preparation, microstructure and mechanical properties of ZTA particles reinforced Fe matrix composites (ZTAP/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 (δA) were determined as well. The nickel-chromium double-layer coated ZTAP of core-shell structure was prepared by electroless plating and multi-arc ion plating technologies. The modified ZTAP is consisted of the α-Al2O3, t-ZrO2, α-Cr and γ-Ni phases. In addition, the compressive strength of ceramic preforms is high due to a compact sintering neck formed among ZTAP during high temperature sintering. The preferred sintering process for ZTA ceramic preforms is determined as 1350 °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 ZTAP/Fe composites. The interface contains double transition layers, which refer to silicate and CrFe phases, respectively. The H, E and δA of interfacial double transition layers were measured by the nano-indentation method, the values of which are situated between the ZTAP and iron matrix.

To investigate the erosive wear-corrosion behavior of ZTAP ceramic reinforced high chromium cast iron matrix composites in two types of sand at various rotational speeds, the ZTAP/Fe composites were fabricated. The interface characteristics, erosion wear-corrosion and erosive wear mechanism have been investigated in a slurry condition at various erosion rotational speeds. The chemical composition of the matrix material was determined using a spark spectrometer. SEM, TEM, 3D laser scanning microscope and AFM were used to analyze the microstructure characteristics and worn surface morphology of the composites. Furthermore, the wear loss rate and relative erosive wear resistance of ZTAP/Fe composites and Cr15 standard specimen measurements were conducted. The results showed that the interface between the ZTAP ceramics and the Cr15 matrix exhibits a continuous transition layer without visible defects and close contacts. In the case of SiO2 and SiC abrasive sand, the wear rate of ZTAP/Fe composites and Cr15 standard specimens increases with erosion time. The wear rate of ZTAP/Fe against SiO2 sand is lower than that of against SiC sand. ZTAP/Fe composites was found to exhibit a better corrosion resistance property than that of Cr15 standard specimens.

NiCr–Mo–Bi2O3/TiO2 composites were prepared by vacuum hot-press sintering technology. The oxides of Bi4Ti3O12, Cr2O3 and Ti2O3 were formed by the reaction of Cr, Bi2O3 and TiO2 during the sintering process. The intensity of Bi4Ti3O12, Cr2O3 and Ti2O3 diffraction peaks became higher with the incremental content of Bi2O3 and TiO2. Mo element was mainly distributed in the matrix, which had the effect of solid solution strengthen in the composites. The microhardness and yield strength improved with addition of Mo. With Bi2O3 and TiO2 adding, the microhardness obviously increased. The microhardness of NiCr–10Mo–30Bi2O3/TiO2 composite was the highest of 491.6 HV. Nevertheless, the yield strength and ultimate strength significantly decreased. It may be caused by cracks in the interface between metallic oxides and matrix, where stress concentration would occur. The NiCr–10Mo–20Bi2O3/TiO2 composite had the lowest wear rate of 2.1 × 10−5 mm3/Nm, which was probably due to the oxidation layer was very dense and was very hard to shed in the process of friction. The composites after adding of Bi2O3 and TiO2 presented the excellent tribology property due to the fact that the Bi4Ti3O12 formed on the worn surfaces which had been proved to be an outstanding lubricant at high temperature.

BaO and TiO2 reacted and produced BaTiO3 in the process of sintering. As a result, the diffraction peaks of BaTiO3 became stronger with the increasing BaO/TiO2 contents. The diffraction peaks of NiAl shifted smaller angle to left with the addition of BaO/TiO2. Meanwhile, the lattice distortion obviously occurred in the composite structure. The composites with the addition of BaO/TiO2 presented high microhardness and yield strength as well. The composite with 20% BaO/TiO2 had the highest microhardness value and yield strength of 474.5 HV and 2786 MPa, respectively. The friction coefficient and wear rate of the composites decreased with the addition of BaO/TiO2 and the NiAl-30% BaO/TiO2 composite had the lowest friction coefficient at 800 °C test temperature. The BaTiO3 was decomposed to BaO and TiO2 during high temperature sliding.

The work of adhesion (Wad), interfacial fracture toughness ( K I c int ), and electronic structure of the Fe(100)//MCs(100) (M = Ti and V) interfaces have been investigated by means of first-principles calculations. Considering two types of interfaces (type 1 and 2), two MCs (TiC and VC) and three different atomic stacking sequences (Fe-on-M, Fe-on-C and Bridge), totally twelve candidate interfacial configurations were analyzed. It is found that the Wad decreases with the order of Fe-on-C > Bridge > Fe-on-M. With the larger Wad, the type 2 Fe//MCs interfaces are more stable than type 1 Fe//MCs interfaces, in which the Fe-on-C site for type 2 Fe//VC interfaces belongs to the most stable interfacial configuration. Based on the Griffith's theory, the mechanical failure of both type 1 and type 2 Fe//TiC interfaces are more inclined to initiate at the interface. While for the Fe-on-C and Bridge site of both type 1 and type 2 Fe//VC interfaces, the mechanical failure will occur at the VC bulk phases rather than at the interface. Besides, the interfacial fracture toughness of Fe-on-C site for the type 2 Fe//VC structure is the best. The interfacial bonding character of Fe-on-C site for both Fe//TiC and Fe//VC interfaces have been investigated based on the electronic density of states and charge density difference. A mixed covalent/ionic/metallic bonding is revealed between iron and transition metal carbides. Further analysis of mulliken population and magnetic moment of interfacial atoms indicates that the Fe//VC interfaces show higher bonding strength than Fe//TiC interfaces.