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In this paper, the dry cutting performance of Al2O3/TiC-based ceramic composites with nanoCaF2 was studied. Compared with the Al2O3/TiC ceramic tool, the Al2O3/TiC/CaF2 ceramic tool has lower cutting force, cutting temperature and surface roughness when milling 40Cr hardened steel. Three cutting parameters of cutting speed, feed per tooth, and cutting depth were used to conduct orthogonal experiments to study its changing trend. Through testing of cutting force, cutting temperature and surface roughness, and by comparison with ceramic tools without nanosolid lubricant added, the order of influence of three cutting parameters on cutting force, cutting temperature and surface roughness was obtained. The experimental results showed that the cutting force, cutting temperature and surface roughness of Al2O3/TiC/CaF2 ceramic tools containing nanoCaF2 werebetter than those of Al2O3/TiC ceramic tools. The cutting force, the cutting temperature, and the surface roughness were respectively reduced by 16.5%, 25.8% and 43% compared to when no solid lubricant was added. In addition, after adding solid lubricant, the effect of cutting depth on cutting force was significantly reduced. The average friction coefficient of the tool rake surface was 31.1% lower than that of ceramic tools without solid lubricant. In order to explain this phenomenon, through scanning electron microscopy (SEM) scanning and energy spectroscopy (EDS) elemental analysis, the wear reduction mechanism of solid lubricants was analyzed, that is, during the cutting process, nanosolid lubricants precipitated and formed lubricating film on the rake surface of the tool to reduce the friction coefficient. This was also the main reason for reducing the cutting temperature.

The microstructure and corrosion resistance in H2S environments for various zones of X80 pipeline steel submerged arc welded joints were studied. The main microstructures in the base metal (BM), welded metal (WM), coarse-grained heat-affected zone (CGHAZ), and fine-grained heat-affected zone (FGHAZ) were mainly polygonal ferrite and granular bainite, acicular ferrite with fine grains, granular bainite, ferrite, and martensite/austenite constituents, respectively. The corrosion behavior differences resulted from the microstructure gradients. The results of the micro-morphologies of the corrosion product films and the electrochemical corrosion characteristics in H2S environments, including open circuit potential and electrochemical impedance spectroscopy, showed that the order of corrosion resistance was FGHAZ &gt, BM &gt, WM &gt, CGHAZ.

Al (OH)3 coated CaF2 composite powder was prepared by coating Al (OH)3 on surface of micro-sized CaF2 particles using heterogeneous nucleation method. Influence of Al3+ concentration, PH value and reaction temperature was studied. The result reveals that CaF2 particle was uniformly coated with a layer of Al (OH)3 and Al3+ concentration, pH value and reaction temperature are the main factors that affect coating result. Optimum technological conditions are Al3+ concentration of solution before reaction at 0.15 mol/L, pH value at 7.5 and temperature at 75 oC.

In the present study, Ti (C,N)/Al2O3nanocomposite ceramic die material was fabricated through adding nanosize Ti (C,N) powders into micrometer Al2O3matrix by vacuum hot-pressing technology. Effects of the hot press sintering process on mechanical property and microstructure of the nanocomposite ceramic die material were investigated. The optimum hot-pressing technology with the sintering temperature of 1650°C, time duration of 15min and pressure of 30MPa was achieved. The microstructural morphology of the material was also analyzed. It reveals that the intergranular/intragranular microstructure and the resulted intergranular/transgranular fracture mode are the main causes for strengthening and toughening in the nanocomposite ceramic die material.

Ti (C,N)/ZrO2/WC nanocomposite cermet die materials were fabricated by vacuum hot pressing process, the materials have better comprehensive mechanical properties. The friction and wear properties of Ti (C,N)-based nanocomposite cermet die materials were studied, and the worn surfaces microstructure were observed and analysed by SEM and XRD. The experimental results showed that when the rotate speed was higher, the coefficient of friction of the developed cermet die material, which is 0.3-0.4, was lower than that without the addition of nanoZrO2 and micrometer WC. The main wear mechanisms were abrasive wear, oxidation wear and adhesive wear.

The composition, processing technology, mechanical property and engineering performance of ceramic materials such as cermet, ZTA, TZP, TZP/Al2O3, PSZ, Si3N4 and Sialon, etc, have been predominantly summarized when they are used as die materials in various operations such as drawing, extrusion, punching and stamping etc. The problems existed in the research and application of ceramic die materials are discussed, and the perspectives in the application of ceramic die materials are pointed out. It is concluded that advanced ceramic material is one of the most promising die materials because of its high hardness, high wear resistance, superior high-temperature property and chemical stability and good engineering performance, compared with other die materials such as die steel and cemented carbides. It is proposed that nano composite and functionally gradient ceramic, surface modification technology with ceramic, optimal design of die structures and die reliability research, etc. are all the potential and effective methods in the improvement of mechanical property and engineering performance of ceramic die materials.