Application of HIP Hot Isostatic Pressure Sintering Furnace in Special Ceramic Materials
Special ceramics include structural ceramics and functional ceramics. In order to enhance the toughness of ceramics, fibers or whiskers are usually introduced into the ceramic matrix. However, due to the high sintering temperature and long sintering time, the surface strength of the fibers and whiskers often deteriorates, and even reacts with the matrix chemically, thus losing the role of reinforcing and toughening. The sintering temperature and holding time are greatly reduced by hot isostatic pressing sintering process, and ceramic matrix composites reinforced by fibers or whiskers with excellent properties can be obtained. For example, SiC whisker reinforced SiC ceramics with relative density up to 91.5% were obtained by hot isostatic pressing sintering at 1085 degrees Celsius. The room temperature flexural strength and fracture toughness of SiC whisker reinforced SiC ceramics reached 595 MPa and 6.7 MPa.m, respectively. In addition, the fracture toughness of ceramics can also be improved by adding second phase particles into the ceramic matrix. However, it is difficult to sinter because of internal stress during sintering, which is solved by hot isostatic pressing sintering. For example, reinforcing AL2O3 with titanium particles, hot isostatic pressing sintering of ceramics has successfully prepared fully dense composite ceramics.
The hot isostatic pressing process was adopted. Single-phase and multiphase nanostructured ceramics have been prepared by Shanghai Silicate Research Institute. The results show that the sintering time is 1 h at 1850 degrees Celsius and 200 MPa. Single-phase SirN4/SiC nanoceramics with uniform and compact grain size < 100 nm can be obtained, and composite SirN4/SiC nanoceramics with uniform and compact structure can be obtained by sintering at 1 750 oC and 150 MPa for 1 h. The research on the preparation of Si 3N nano-ceramics by sintering-hot isostatic pressing process in Rutgers University has also achieved good results.
In order to improve the high temperature resistance and corrosion resistance of metals, metal-ceramic composites formed by coating a layer of ceramics on metal surface by plasma technology are mainly mechanically bonded, and there are a large number of air holes in the coating, thus affecting the impact resistance and corrosion resistance of materials. If the surface of metal coated with ceramic coating is coated and sealed in vacuum, hot isostatic pressing is applied. Not only can the ceramic coating be completely dense, but also a layer of cermet phase will be formed between the ceramic coating and the metal matrix due to diffusion. The metallurgical bonding between coatings and metals is realized, and the composite material has ideal bonding strength and excellent comprehensive properties.