High Strength Silicon Nitride Prepared with Eutectic Flux Additions

1977 ◽  
pp. 391-392 ◽  
Author(s):  
J. D. Venables ◽  
D. K. McNamara ◽  
R. G. Lye
Keyword(s):  
Silicon Nitride ◽  
High Strength

Development and Fabrication of Silicon Nitride Components for Ceramic Gas Turbine

1997 ◽  
Author(s):  
Keisuke Makino ◽  
Ken-Ichi Mizuno ◽  
Toru Shimamori
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Blades ◽  
High Strength ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Spark Plug ◽  
Power Turbine

NGK Spark Plug Co., Ltd. has been developing various silicon nitride materials, and the technology for fabricating components for ceramic gas turbines (CGT) using theses materials. We are supplying silicon nitride material components for the project to develop 300 kW class CGT for co-generation in Japan. EC-152 was developed for components that require high strength at high temperature, such as turbine blades and turbine nozzles. In order to adapt the increasing of the turbine inlet temperature (TIT) up to 1,350 °C in accordance with the project goals, we developed two silicon nitride materials with further unproved properties: ST-1 and ST-2. ST-1 has a higher strength than EC-152 and is suitable for first stage turbine blades and power turbine blades. ST-2 has higher oxidation resistance than EC-152 and is suitable for power turbine nozzles. In this paper, we report on the properties of these materials, and present the results of evaluations of these materials when they are actually used for CGT components such as first stage turbine blades and power turbine nozzles.

Hot Rolling Steels and Super Alloys with Silicon Nitride Tools

2010 ◽  
Vol 65 ◽  
pp. 92-99
Author(s):  
R. Danzer
Keyword(s):  
Silicon Nitride ◽  
Fatigue Cracks ◽  
High Strength ◽  
Ceramic Tool ◽  
Silicon Nitride Ceramic ◽  
Small Surface ◽  
Metal Parts ◽  
Improved Performance ◽  
Montanuniversität Leoben ◽  
Super Alloy

Tools for rolling steels and super alloys, which are nowadays in general made from steel or cemented carbides, suffer from wear and/or from surface cracking caused by thermal fatigue. New tools made from silicon nitride show improved performance in respect to thermal shock loading and wear. But their low toughness manifests also a high risk of brittle failure. Nevertheless the successful use of silicon nitride rolls with having more than a manifold lifetime (compared to the conventional solutions) has been reported in the last years [1 -3]. In this paper earlier work of the Institut für Struktur- und Funktionskeramik at Montanuniversität Leoben on highly loaded silicon nitride rolls is summarized, where the limits of the Application of silicon nitride rolling tools are discussed. On the extreme example of rolls for super alloy wire rolling the behaviour of small surface cracks in the roll track is discussed. It is shown that – for the investigated conditions - rolling high strength steel wires is manageable but rolling of super alloy wires will cause the growth of fatigue cracks, which may destroy the rolls after some tons of rolled wire. A not trivial problem to be solved is the connection of the ceramic tool with the metal parts of the roll stand. Thermal strains of the metal parts can be several times larger than those of the silicon nitride ceramic and can therefore cause very high thermal misfit strains, even if the heating of metal parts seems to be modest. This case is discussed on the example of a catastrophically failed ceramic tool. This clearly shows that not only the tool but also the joint of the tool to the rest of the machinery has to be designed carefully. In summary this work demonstrates that a successful use of silicon nitride ceramic tools for cold and hot forming of metals and alloys is possible.

High-strength silicon nitride ceramics obtained by grain-boundary crystallization

1991 ◽  
Vol 26 (20) ◽  
pp. 5513-5516 ◽  
Author(s):  
K. Komeya ◽  
M. Komatsu ◽  
T. Kameda ◽  
Y. Goto ◽  
A. Tsuge
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
High Strength ◽  
Nitride Ceramics

Dislocation loops in α-silicon nitride single crystals

1992 ◽  
Vol 50 (1) ◽  
pp. 342-343
Author(s):  
H. Suematsu ◽  
J. J. Petrovic ◽  
T. E. Mitchell
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Single Crystals ◽  
Mass Production ◽  
High Strength ◽  
Deformation Characteristics ◽  
Dislocation Loops ◽  
Production Lines ◽  
Compressor Rotor ◽  
Structural Applications

Silicon nitride(Si3N4) is well known to be a most promising ceramic material for high temperature structural applications. It has high strength even at 1200°C and its fracture toughness is about 5 to 7 MPa•m½. Si3N4 has been manufactured on mass production lines as the compressor rotor for turbo chargers. For high temperature use, it is important to know the deformation characteristics of the material and the role played by dislocations and other defects. However, research on the nature of defects in Si3N4 has been limited considering the importance of Si3N4. In this study, we have examined defects in single crystals of Si3N4.

Failure Analysis of Si3N4 Rolls for Wire Hot Rolling by Numerical Simulation of Thermal and Mechanical Stresses

2005 ◽  
Vol 290 ◽  
pp. 94-101 ◽  
Author(s):  
Markus Lengauer ◽  
Robert Danzer ◽  
Domagoj Rubeša ◽  
Walter Harrer ◽  
W. Zleppnig
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Silicon Nitride ◽  
Hot Rolling ◽  
Rolling Mill ◽  
Subcritical Crack Growth ◽  
Thermal Stresses ◽  
High Strength ◽  
Induced Stresses ◽  
Observed Damage

Silicon nitride rolls for wire hot rolling have been tested in the rolling mill. After short employment for processing of ultra-high strength materials, cracks appeared in the roll calibre, which limited further application of the rolls. In order to find out possible causes for the damage, relevant mechanical properties of the roll have been determined and thermally and mechanically induced stresses were assessed by numerical simulation. It has been found that thermal stresses are of little relevance, whereas mechanically induced stresses are high enough to enhance subcritical crack growth resulting in the development of the macroscopic cracks, so that the observed damage of the rolls could have been adequately explained. One further result of the analysis was that flaws induced by grinding are decisive for the service time of ceramic rolls, so that special attention has to be paid to the machining of the roll calibre.

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