Research status and development trend of spark plasma sintering technology

---

SPS technology research status

Powder metallurgy technology has a series of advantages such as short process, energy saving, low cost, and less processing. It can freely assemble material structures to precisely control material properties, which is an important development direction of green manufacturing technology. The spark plasma sintering technology has the advantages of fast speed, low temperature, energy saving, environmental protection, easy operation, and excellent product performance. It is widely used in metals, ceramics, cemented carbide, and functionally gradient materials. It is currently the most concerned new preparation technology and One of the crafts.

SPS technology is a rapid prototyping preparation method in which pulsed current is directly applied between the mold and the powder particles or in the bulk sample for sintering or connection. It is a new rapid sintering process that has been studied since the 1990s. Compared with the traditional hot pressing sintering technology, in addition to energizing to generate Joule heat and plastic deformation caused by pressure to promote sintering, a DC pulse voltage generated by a special power source is also applied to the compacted powder sample, so it will produce a unique Promote sintering phenomenon (this part is described in detail in the previous public number article, and I will not repeat it in this issue).

SPS equipment mainly includes pressure system, vacuum system, water cooling system, temperature measurement system, power supply and control system, etc. Due to SPS’s unique technology and obvious technological advantages, since Japan introduced SPS equipment that can be used for new material research and development and industrial production in 1990, SPS technology and equipment have advanced by leaps and bounds and opened up new areas of manufacturing.

The experimental equipment developed and produced by our company can process samples with a diameter of 300mm, the pressure can reach 5T-400T, and the maximum output current is 3000A-48000A. The equipment has strong versatility and can meet the requirements of use from the research and development stage to the product trial production stage.

SPS technology development trend
1. Industrialization
Compared with traditional sintering methods, SPS technology has obvious advantages in saving energy and time, improving production efficiency, and controlling product performance. At present, Japan has realized the industrial application of SPS, which is mainly used to produce magnetic materials and hard materials. Alloys, functionally gradient materials, etc. For example, Japan’s Ota Seiki has achieved SPS mass production of 100% WC superhard materials, and the products have been supplied to more than 40 manufacturers of motors, electronic parts, tools, molds, etc. in Japan and abroad. However, the domestic SPS technology is still in the laboratory research stage, and it is mostly used for the preparation of new materials and the research of technology.

2. Diversified shapes of sintered bodies
Due to the limitation of sintering mechanism and graphite mold, the samples prepared by SPS are mainly simple cylinders, it is difficult to prepare workpieces with complex shapes, and cannot meet the needs of actual engineering.

SPS technology development trend

3. Performance optimization of sintering mold
Graphite has high temperature resistance, excellent electrical and thermal conductivity, chemical stability, thermal shock resistance, good lubrication and wear resistance, and is used as a common mold material for SPS. However, graphite materials have low strength, short lifespan and easily cause pollution to sintered materials. At present, there have been reports of cemented carbide molds, conductive ceramic molds, carbon fiber graphite molds, etc., but there are problems such as high temperature and easy deformation and high price. Therefore, in order to make better use of SPS technology, further development of higher strength and reuse rate is required. High, pollution-free new mold material.

4. Further development combined with finite element simulation
In the special working environment of SPS, the general method cannot accurately analyze the sintering process, forming mechanism, influencing factors, etc. There are also certain errors in obtaining the temperature, displacement and other parameter changes in the sintering process. Therefore, finite element simulation has become the new SPS One of the research methods. It has been reported that the sintering process can be simulated by ABAQUS, MATLAB, MSC.MARC and other software, and the temperature field distribution and electric field distribution during the sintering process can be obtained, and the specific influence of each sintering parameter on the sintering process can be analyzed. Preliminary prediction of research and test results and theoretical guidance of production are of great significance.

Since the appearance of spark plasma sintering technology, it has developed rapidly due to its low temperature, short time and high efficiency. Important research results have been made in the preparation of refractory metals, hard alloys, ceramic materials, high thermal conductivity materials and other fields. However, the sintering mechanism of the intermediate process is still controversial, and a large number of experiments and theoretical studies are still needed to improve it. Further exploration is needed in terms of molds and processes.