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19THE KEY ROLE OF STRUCTURAL AND PHASE COMPOSITION FOR FORMATION GRADED MATERIALS BY SHS -COMPACTION TECHNOLOGY
Z. Aslamazashvili*", G. Oniashvili", G. Zakharov", G. Tavadze", and M. Chikhradze"
aTavadze Metallurgy and Mateials Science Institute, Tbilisi, 0186 Georgia *e-mail: oniash@gtu.ge
DOI: 10.24411/9999-0014A-2019-10012
The goal of the work is to define key aspects of structure and phase composition for obtaining graded materials by self-propagating high-temperature synthesis (SHS)-compaction technology, working under high dynamic loadings, where the adhesion strength between the layers is not worse than the strength of its ceramic and metal-ceramic layers [1, 2].
In order to have good adhesion between the layers it is necessary not to have sharp border between them and to have smooth transformation. For the realization of above said, diffusion process is necessary. For the process high temperature and time are necessary. Proceeding from the peculiarity of SHS-compaction high temperatures are generated, but at the same time process is very rapid and there is no enough time for diffusion process. Form obtaining well consolidated samples by mentioned technology, it is necessary to have maximal velocity of the synthesis front.
Based on results of experiments carried out in Ti-B, Ti-B-N, Ti-B-N-C, Ti-C, and Ti-Cr-C systems, the following peculiarities of structure and phase composition of layers were defined [3]:
- The neighboring ceramic or metal-ceramic layers of graded material should contain at least one or more similar phases;
- In transient zone, brittle low-strength chemical compounds must not form;
- The metal layer, if it exists, must comply with the following requirements: we should select the compound, where wetting angle with ceramic or metal-ceramic material must be no more than 90°;
- Metal layer should have the same content as ceramic layer or metal components in metal-ceramic layer;
- Metal layer should have the same content as metal alloy included in metal-ceramic layer;
- When obtaining the graded material, the synthesis velocities of exothermic layers are the same;
The analysis of experiments showed that if one of the above listed conditions is realized, we can obtain graded material with smooth transient zone and good adhesion.
Graded material 1 (Fig. 1): one of the layers is synthetic composite ceramic material (SCCM-1) based on Ti-B-N system. The second layer is Ti-B-C-N-based SCCM-2. The SCCM-1 consists of the following phases: TiB, TiN (small amount), and Ti2N. The second layer SCCM-2 consists of the following phases: TiB, TiCN (small amount), Ti2CN, and TiB2.
Graded material 2 (Fig. 2): the first layer is SCCM-1 based on Ti-B-N system, the second layer is metal-ceramic material TiB0.6 based on Ti-B system. SCCM-1 consists of TiB2 (small amount), TiB, TiN (small amount), and Ti2N. TiB0.6 layer consists of TiB and Ti. Those 2 layers have one common phase TiB. As a result, the graded material is obtained. The outer surfaces have different properties, but the transition layer from one to another is smooth. Therefore, the material is characterized by high adhesion strength between the layers.
ÏSHS2019
Moscow, Russia
Fig. 1. Microstructure of transient zone of graded material between SCCM-1 and SCCM-2.
Fig. 2. Microstructure of transient zone of graded material between SCCM-1 and TiB0.6.
Graded material 3 (Fig. 3): the first layer is SCCM-2 based on Ti-B-N-C system, the second layer is metal-ceramic TiB0.6 based on Ti-B system. SCCM-2 contains TiB, TiCN (small amount), Ti2CN, and TiB2. The second layer consists of TiB and Ti. Those 2 layers have one common phase TiB. As a result, the graded material is obtained. The outer surfaces have different properties, but the transition layer from one to another is smooth. Therefore, the material is characterized by high adhesion strength between the layers.
Graded material 4: the first layer is SCCM-1 based on Ti-B-N system, the second layer is metallic Ti (Fig.4.). One of the components of the SCCM-1 layer of initial chasm is Ti, and after the synthesis it consists of the phases: TiB, Ti2N, TiB2 (small amount), and TiN (small amount). Both layers have Ti as one of the components in initial chasm, as a result the graded material whose outer surfaces have different properties is obtained. The transition between the layers is smooth. The material is characterized by good adhesion between the layers.
Fig. 3. Microstructure of transient zone of Fig. 4. Microstructure of transient zone of graded material between SCCM-2 and graded material between SCCM-1 and Ti.
TiB0.6.
Graded material 5 consists of SCCM-2 based on Ti-B-N-C system and metallic Ti. Both layers have Ti as one of the components in initial chasm, as a result the graded material whose outer surfaces have different properties is obtained. The transition between the layers is smooth. The material is characterized by good adhesion between the layers.
Graded material 6: the first layer is SCCM-1 based on Ti-B-N system, the second is metallic-ceramic TiC-based layer. SCCM-1 consists of TiB2 (small amount), TiB, TiN (small amount), and Ti2N. In this layer the velocity of synthesis front V is ~ 10 mm/s. The second layer consists of the following phases: TiC and metal phase, which can be Ni, Fe or steel, for example,
X18H15. Those 2 layers do not have any common or similar phases, but the velocity of the synthesis front is same (V ~ 10 mm/s). As a result, the graded material is obtained. The outer layers have different properties, but the similarity of synthesis velocity provides good mixing and combination of components on the border. The transition between the layers is smooth, which provides the high adhesion strength between the layers. Figure 5 shows the microstructure of transient zone of material 6.
Graded material 7: one of the layers contains the phases TiC, C3C2, and metallic phase which may be Ni, Co or TiC, &3C2, Cr23-xFexC6, and metallic phase which can be Fe or steel (X18H15). In this layer the velocity of synthesis front is V ~ 18 mm/s. The other layer is metal-ceramic phase consisting of TiC and metal phase (Ni, Fe, and steel X18H15). Those 2 layers have common phases and at the same time the velocities of synthesis front in both layers are the same V ~ 18 mm/s. As a result, graded material is obtained. The outer layers have different properties, but the similarity of synthesis velocity provides good mixing and combination of components on the border. The transition between the layers is smooth, which provides the high adhesion strength between the layers. Figure 6 shows the microstructure of transient zone of graded material between TiC/Cr3C2-X18H15 and TiC-X18H15.
Fig. 5. Microstructure of transient zone Fig. 6. Microstructure of transient zone of between SCCM-1 and metal-ceramic graded material between metal-ceramic TiC-Steel (X18H15). TiC/Cr3C2-X18H15 and TiC-X18H15.
1. Z. Aslamazashvili, G. Zakharov, G. Oniashvili, G. Urushadze, G. Mikaberidze, G. Tavadze, M. Chikhradze, Microstructure peculiarities of metal-ceramic materialz of Ti-Cr-C system by SHS-compaction, Book of Abstracts SHS, 2017, p. 37.
2. Z. Aslamazashvili, G. Zakharov, G. Oniashvili, N. Aslamazashvili, G. Mikaberidze, M. Chikhradze, G. Tavadze, Peculiarities of microstructure of ceramic materials in obtained in Ti-B-C-N system by SHS, p. 42.
3. Patent: AP 2017 14618, Saqpatenti, Georgia, 2017.
