Technical Information

D-2 Cermet Sintering Technology

D-2 Cermet Sintering Technology

Toshiba Machine has developed the cermet material which is superior in corrosion resistance and wear resistance, and applies it to a variety of parts such as a barrel for the extruder (upper left photo) and sleeve for the die casting machine, making full use of our special sintering technology. We introduce real life examples of employing such material to the barrel for extruder and plunger sleeve for aluminum die casting machine to dramatically extend the service life, compared with the previous barrels and sleeve.

[Platform]
D. Material technology
[Applications]
Extruding machine, Die casting machine

[Technical Highlights]

  • Our cermet excels in corrosion and wear resistance and allows cutting.
  • The life of cermet sleeve is about 20 times, compared with that of the previous sleeve.
  • 1.5mm-thick lining of cermet material is done inside the sleeve.

1. Introduction

Toshiba Machine manufacture various molding machines for plastic injection molding and extrusion, aluminum (Al) die-casting, etc. In either machine, material has to be heated to have fluidity and pressurized mechanically, and machine parts for such motions require corrosion resistance and wear resistance. For instance, In the barrel of the twin-screw extruder compounding and granulating plastic material, corrosion by decomposition product which is caused from material resin and additive, and wear by inorganic fiber contained in material will occur at the same time. In the plunger sleeve of the Al die casting machine also, erosion by molten Al and wear by sliding with the plunger tip are caused simultaneously. For the parts used under such hostile environment, lining of cermet material (*1) superior in corrosion resistance and wear resistance is made on the steel surface of the structure to extend their service life.
To make lining of cermet material on the steel surface, technologies of thermal spraying, hot isostatic pressing (HIP) and centrifugal casting are generally used. We perform lining of our special cermet material on the steel surface, using our special manufacturing technique and based on the material development and sintering technology accumulated for the past 30 years. Now, we introduce the features of our cermet material and performance when used for the machine parts.
*1 Compound material produced by sintering ceramic and metal powders.

2. Features of our cermet

Fig. 1 Cermet structure after lining treatment

Fig. 1 Cermet structure after lining treatment

Our cermet has a structure where fine boride is dispersed on the Ni alloy foundation and it excels in corrosion and wear resistance and allows cutting operation. The photo of the structure is shown in Fig. 1.
This material is produced by sintering, and at the same time with sintering, steel surface can be joined. Steel base material and cermet are coupled metallurgically, and due to almost identical thermal expansion coefficient of the steel and cermet, the cermet layer will not peel off or fall away be applied. This cermet can as the lining of internal surface of a pipe with small inner diameter, which cannot be addressed by thermal spraying, and the lining of a complex profile such as the barrel of twin-screw extruder. It will not require use of a special furnace as in HIP and is very economical.

3. Sleeve of die casting machine

Fig. 2 External view and sectional photo of sleeve

Fig. 2 External view and sectional photo of sleeve

In Al die casting, molten metal is ladled from the holding furnace and poured into the plunger sleeve, then molten metal is injected into the dies, using the plunger tip. Though nitride hot work die steel is generally used for the sleeve material and in most occasions the sleeve surface is eroded by molten Al and the sleeve life ends.
Erosion is expedited when Al diffuses in Fe of base material, then formation and exfoliation of Fe-Al compound are repeated. We made lining of about 1.5mm-thick highly erosion resistant cermet on the inner surface of the sleeve, thus realizing long life of the sleeve. External view and sectional photo of the sleeve are shown in Fig. 2.

Fig. 3 Schematic diagram of erosion test

Fig. 3 Schematic diagram of erosion test

Erosion resistance of our cermet against molten Al is as follows. Fig. 3 shows the schematic diagram of erosion test. A test piece was rotated in molten Al, and erosion volume against immersion area was compared as erosion amount. Al molten metal was AC4C whose temperature was 720°C, peripheral speed of the test piece was 0.8m/s and the testing lasted for two hours.

Fig. 4 Results of erosion test

Fig. 4 Results of erosion test

Erosion amounts of our cermet and traditional SKD61 nitride material are shown in Fig. 4. Erosion amount of our cermet is about 1/25, compared with the SKD61 nitride material. Though nitrides such as Fe3N and Fe4N are formed on the surface of the SKD61 nitride material and contribute to suppress the reaction with molten Al, these nitrides are dissolved easily at molten metal temperature. Meanwhile, with our cermet Mo2NiB2 is dispersed in Ni alloy foundation and it contribute to suppress the reaction with molten Al.

Fig. 5 Results of field test

Fig. 5 Results of field test

Next, we report the results of field test done during actual operation of the plunger sleeve. The casting conditions are shown in Table 1 and the results of field test done on the four sleeves are shown in Fig. 5. The plunger sleeve made of our cermet has extended its life by about 20 times, compared with that of the traditional sleeve and has demonstrated stable performance.

*2: The number of shot counts up to the life end were determined by the customer based on the defect rate.

Table 1 Casting conditions
ItemConditions
Sleeve profileOuter diameter 105 × inner diameter 60 - length 347mm (temperature control at 150°C)
Molten metal Equivalent to ADC12, 690°C, 1 - 1.2kg/shot

4. Conclusion

When lining of our cermet is made on the parts of the plastic molding machine and die casting machine, which require corrosion resistance and wear resistance, their life time can be increased remarkably. This will lead to reduction of consumable parts and maintenance cost and improvement of productivity and largely contributes to cost reduction per shot. We will continue supplying such material which maximize the benefit for the customers by developing the material technology.