Oxidation resistance of diamonds with molybdenum disilicide coatings

1984 ◽  
Vol 23 (1) ◽  
pp. 60-62
Author(s):  
V. F. Grishachev ◽  
V. P. Maslov ◽  
�. V. Prilutskii ◽  
A. A. Semenov-Kobzar'
Keyword(s):  
Oxidation Resistance ◽  
Molybdenum Disilicide

Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings

1994 ◽  
Vol 52 ◽  
pp. 538-539
Author(s):  
H. Kung ◽  
T. R. Jervis ◽  
J.-P. Hirvonen ◽  
M. Nastasi ◽  
T. E. Mitchell ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Matrix Material ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Cross Sectional ◽  
Good Oxidation Resistance ◽  
Structural Applications

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.

Molybdenum disilicide coating on steel and its oxidation resistance

1982 ◽  
Vol 1 (1) ◽  
pp. 19-22 ◽  
Author(s):  
Seiji Motojima ◽  
Akiyoshi Fujimoto ◽  
Kohzo Sugiyama
Keyword(s):  
Oxidation Resistance ◽  
Molybdenum Disilicide ◽  
Molybdenum Disilicide Coating

Mechanically Activated Combustion Synthesis of Molybdenum Silicides and Borosilicides

2014 ◽  
Vol 1760 ◽  
Author(s):  
Mohammad S. Alam ◽  
Alan A. Esparza ◽  
Evgeny Shafirovich
Keyword(s):  
Mechanical Properties ◽  
Oxidation Resistance ◽  
Power Plants ◽  
Exothermic Reaction ◽  
Molybdenum Disilicide ◽  
Combustion Products ◽  
Shs Compaction ◽  
Molybdenum Silicides ◽  
High Oxidation ◽  
High Oxidation Resistance

ABSTRACTMolybdenum silicides and borosilicides are promising structural materials for advanced power plants. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at high temperatures. For example, molybdenum disilicide (MoSi2) has excellent oxidation resistance and poor mechanical properties, while Mo-rich silicides such as Mo5Si3 (called T1) have much better mechanical properties but poor oxidation resistance. One approach is based on the fabrication of MoSi2−T1 composites that combine high oxidation resistance of MoSi2 and good mechanical properties of T1. Another approach involves the addition of boron to Mo-rich silicides for improving their oxidation resistance through the formation of a borosilicate surface layer. In particular, Mo5SiB2 (called T2) phase and alloys based on this phase are promising materials.In the present paper, MoSi2−T1 composites and materials based on T2 phase are obtained by mechanically activated self-propagating high-temperature synthesis (MASHS). To obtain denser products, the so-called SHS compaction (quasi-isostatic pressing of hot combustion products) has been employed. Thermal analysis has shown that SHS compaction significantly improves the oxidation resistance. Self-sustained combustion of Mo/Si/B mixtures for the formation of T2 phase becomes possible if the composition is designed for adding a more exothermic reaction of MoB formation. These mixtures exhibit spin combustion. Oxidation resistance of the obtained multi-phase Mo−Si−B materials is independent on the concentration of Mo phase in the products. The “chemical oven” technique has been used to obtain a single Mo5SiB2 phase and an alloy consisting of α-Mo, Mo5SiB2, and Mo3Si phases.

Role of Silica in the Oxidation Resistance of Molybdenum Disilicide

Nature ◽  
1964 ◽  
Vol 203 (4948) ◽  
pp. 967-969 ◽  
Author(s):  
GEORGE TODD ◽  
ERIC PARRY
Keyword(s):  
Oxidation Resistance ◽  
Molybdenum Disilicide

High Temperature Oxidation Behaviors of CNTs/MoSi2 Composites

2014 ◽  
Vol 487 ◽  
pp. 15-19
Author(s):  
He Jian Wu ◽  
Hou An Zhang ◽  
Si Yong Gu ◽  
Jia Lin
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Molybdenum Disilicide ◽  
Protective Film ◽  
Matrix Composites ◽  
Temperature Oxidation ◽  
Good Oxidation Resistance ◽  
Gaseous Products ◽  
Oxidation Behaviors

Molybdenum disilicide (MoSi2) matrix composites with various contents of carbon nanotubes (CNTs) were fabricated by sintering in vacuum at 1550°C for 1 h. The oxidation behaviors of CNTs/MoSi2composites at 1300°C for 200 h in air were studied. Results showed that MoSi2matrix composites with no more than 8 % CNTs in volume had good oxidation resistance at 1300 °C, although addition of CNTs reduced the high temperature oxidation resistance of MoSi2. An approximate linear relationship was found between the weight gain of CNTs/MoSi2composites and the content of CNTs. The oxidation resistance of CNTs/MoSi2composites at high temperature decreased with the increasing of CNTs contents. Since the gaseous products were formed during the oxidation process and escaped from the oxide film, the protective film became loose which offered channels for the oxygen soaking into the composites. Thus the oxidation resistance of CNTs/MoSi2composites was decreased.

Morphologies of Nonadherent Al2O3 and Matching Substrate Surfaces

1972 ◽  
Vol 30 ◽  
pp. 524-525
Author(s):  
C. S. Giggins ◽  
J. K. Tien ◽  
B. H. Kear ◽  
F. S. Pettit
Keyword(s):  
Electron Microscopy ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
Substrate Surface ◽  
Morphological Features ◽  
Thermally Induced ◽  
Oxide Spallation ◽  
Oxidation Resistant ◽  
Induced Stresses ◽  
Substrate Surfaces

The performance of most oxidation resistant alloys and coatings is markedly improved if the oxide scale strongly adheres to the substrate surface. Consequently, in order to develop alloys and coatings with improved oxidation resistance, it has become necessary to determine the conditions that lead to spallation of oxides from the surfaces of alloys. In what follows, the morphological features of nonadherent Al2O3, and the substrate surfaces from which the Al2O3 has spalled, are presented and related to oxide spallation.The Al2O3, scales were developed by oxidizing Fe-25Cr-4Al (w/o) and Ni-rich Ni3 (Al,Ta) alloys in air at 1200°C. These scales spalled from their substrates upon cooling as a result of thermally induced stresses. The scales and the alloy substrate surfaces were then examined by scanning and replication electron microscopy.The Al2O3, scales from the Fe-Cr-Al contained filamentary protrusions at the oxide-gas interface, Fig. 1(a). In addition, nodules of oxide have been developed such that cavities were formed between the oxide and the substrate, Fig. 1(a).

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