Molybdenum Disilicide Coating - Spark Plasma Sintering As Follows:
1. Kuchino so the Mo-Si powder were mixed in terms of atomic ratio of 1:2, into a graphite mold, the graphite mold 6 Pa into the vacuum chamber, subjected to a mold pressure of 40 MPa, and a powder intake pulse current to 0.17 ℃ / s the temperature was raised, the maximum sintering temperature is 1 400 ℃, 600 s-situ synthesis of maintaining density of 99% molybdenum disilicide, molybdenum disilicide dense containing a small amount of SiO2. With molybdenum disilicide powder as raw material, using the same technology is also synthesized material density of 99%, the synthesized materials accelerated oxidation zone (400 ~ 700 ℃) has good resistance to oxidation;
2. Shimizu et SHS process preparation of a powder of molybdenum disilicide, and at 1254 ℃, 30MPa pressure sintering apparatus in the SPS 10 min, were prepared by density reached 97.3%, the grain size is 7.5μm, the Vickers hardness to 10.6 GPa, fracture toughness KIC is 4.5 MPa • m1 / 2, the bending strength of 560 MPa of the material. At 1000 ℃, molybdenum disilicide strength can be maintained at about 325MPa;
3. Krakhmalev first on the raw material powder and other high-energy ball milling, and then use SPS sintering, were given the C40 structure Mo (Si0.75Al0.25) 2, Mo (Si0.75Al0.25) 2/SiC, Mo (Si0. 75Al0.25) 2/0, 10,20,30% (volume fraction) Al2O3 and Mo (Si0.75Al0.25) 2/ZrO2 composite materials.
Mo (Si0.75Al0.25) 2 base material hardness of 14GPa, indentation fracture toughness 1.84Mpa.m1 / 2 around the fracture mainly by cleavage. With 20% of SiC does not improve the hardness, the fracture toughness of the material can be increased to 2 • 48 MPa • m1 / 2, there intergranular fracture surface characteristics; when the Al2O3 content is less than 20%, the hardness of the material and the pressure marks fracture toughness without significant improvement in the fracture cleavage based, and containing 30% Al2O3 composites reduce the hardness of 10.2 GPa, fracture toughness increased to 3.67 MPa • m1 / 2, the fracture surface showed significant intergranular characteristics.
In Mo (Si0.75Al0.25) 2/ZrO2 composite discovered Mo, Mo5Si3, Al2O3 and Mo0.34Zr0.20Si0.46, i.e. Mo (Si, Zr) 2 phase, the hardness is about 14 GPa or so, indentation fracture toughness of 2.69 ~ 2.94 MPa • m1 / 2, and Mo (Si0.75Al0.25) 2 as compared to the fracture toughness increased by 50%, of the synthesis may occur during replacement of Zr Mo (Si, Al) reaction of Al 2:
AlMo(Si,Al)2+ZrO2=ZrMo(Si,Zr)2+Al2O3
Spark plasma sintering (SPS) is a relatively new technology, it can be seen from the above study this process can be obtained relatively dense matrix material and composite material can be prepared, this process in the preparation of molybdenum disilicide has not yet been widely applications, so the material is not very significant performance increase. However, other methods for preparing pure molybdenum disilicide has relatively large increase performance. Because of its high density, at least prevent molybdenum disilicide cryogenic "Pesting" phenomenon, so the future of this process should be a big development.
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