Abstract: Si3N4 powders made from imide process and thermal decomposed at different temperatures have investigated by XPS surface analysis; They were compared with a commercial Si3N4 powder made with nitridation process. Oxygen both in combined form of Si2.2-2.7N2.9-3.7O layer and absorbed form were found on the powder surface, in contrast to Si0.8 N0.8O layer and absorbed form in the case of Si3N4 powders made from Si aitridation.
Abstract: The present work has found that the structure and properties of WC-Co hard metal can be improved by adding some elements or compound (eg. Mo, Cr3C2, TaC etc). The mechanism of the change of the properties was discussed.
Abstract: A new process-WMVE process has been developed after investigations on magnetic separation(M), vacuum loose sintering(V) and hot extrusion (E) of water atomized powders(W) with high oxygen contents. Metallurgical products with properties which are equivalent to those of melted steel can be produced with this process cost-effectively. WMVE process is suitable to be used in present Chinese metallurgical industry.
Abstract: The influence of Cu on the structure and properties of WC-Fe/Co/Ni hard alloy. The experimental results show that the TRS （Transverse Rupture Strength） of WC-Fe/Co/Ni hard alloy can be improved by increasing Cu in alloy. The TRS of the hard alloy appears maximum by adding 0.8% Cu into the alloy. In the alloy Cu increases continuously, TRS of the alloy appears to decrease.
Abstract: Si3N4 ceramics with AZ-type non-toxic, non-oxide additives can be highly densified. In this work densification behavior and mechanism of Si3N4 with AZ-type additives were investigated.
Abstract: Heat treatment changes the structure of the cobalt binder phase and the properties of the WC-Co hardmetals. The higher the cobalt content in the alloy is, the more effective the heat treatment is. The present work has found that the transformation of α-Co to ε-Co can be depressed by quenching the specimens in oil from 1000℃ and hence the transverse rupture strength of these specimens can be increased. During tempering the quenched specimens, new precipitated phases which have dispersion hardening effect on the cobalt binder phase have been observed.
Abstract: A new type of Si3N4 ceramics (ZAN) is developed in our laboratory. Densification of ZAN is promoted by non-toxic, non-oxide AZ-type additives. In this work high temperature (HT) properties and microstructures of ZAN are investigated.
Abstract: The influence of Al on the structure and properties of WC-Fe/ Co/Ni hard alloy was investigated. TRS of the hard alloy can be improved by adding Al agent in the alloy. The TRS of the hard alloy was increased 10% by adding 0.8% A1 is alloy.
Abstract: Vacuum carbothermal reduction of N2-atomized 316L powders and effects of green compact density on hot extrusion and properties of extruded products were investigated. A new capsuleless hot extrusion process of P/M 316L stainless steel was developed and is suitable for present industrial condi tions in China. The basic route of the process is: N2 atomization→vacuum sinte-ring→hot extrusion.
Abstract: The imersion test was performed in H2O and NaCl 5% aqueous solution in order to measure the corrosion weight loss or weight gain of the steel. In combination with their mechanical properties, it is concluded that 40SiMnCrMoV steel can be substituted for 40CrNi3Mo or 40SiMnMoV steel in the case of heavy-duty drill rod.
Abstract: The properties of YA-TZP depend on its microstructures. Optimal combination of mechanical properties with σb =940~1010 MPa and K1c=10.9 MPa√m was obtained as the critical grain size~0,7μm. No strength degradation after aging at 250℃ for 50h. The morphology of different phases in ZrO2, the microcracks and particles of secondary phase wereinvestigated and dislocation networks and lines were found under TEM. Pre-liminary tests show good prospect on application for wire drawing dies.
Abstract: The influence of the rare elements Ce and the RE on the structure and properties of WC-Co hard alloys. It is found that the hard alloy is use of mining indusrty.
Abstract: The microstructure of Si3N4 with non-toxic, non-oxide additive consisting of ZrN and A1N was examined by TEM and EDS. Minor intergranular glassy phase is observed at few triple regions, but is not found in most of grain boundaries in this new Si3N4-based ceramics. The superior HT properties are attributed to the significantly reduced amount of intergranular glassy phase and increase of its softening temperature. Many ZrN particles dispersed in matrix and secondary crystalline phase distributed in triple regions of grain boundaries are observed. Superior mechanical properties are closely related to the micro-structure features. In addition, different superstructures in α'-Si3N4 are found by lattice imaging.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
