Processing Methods for High Reliability Silicon Nitride Heat Engine Components

1995 ◽  
Vol 117 (1) ◽  
pp. 156-160 ◽  
Author(s):  
V. K. Pujari ◽  
D. M. Tracey
Keyword(s):  
Tensile Strength ◽  
Silicon Nitride ◽  
Process Control ◽  
High Reliability ◽  
Heat Engine ◽  
High Strength ◽  
Processing Unit ◽  
Unit Operations ◽  
Engine Components ◽  
Strength Database

The paper discusses highlights of a silicon nitride processing methodology that has been developed in the course of a major four-year DoE funded program in processing for reliability. The program focused on the attainment of high strength and reliability through the identification and subsequent control of strength-degrading flaws introduced during processing unit operations. Process control and NDE methods applied to achieve an optimized process with the potential to produce high-reliability advanced heat engine components are discussed. Concluding remarks are directed to the extensive tensile strength database that has been generated through testing of over 300 tensile rods produced by the optimized process.

scholarly journals Processing Methods for High Reliability Silicon Nitride Heat Engine Components

1993 ◽  
Author(s):  
Vimal K. Pujari ◽  
Dennis M. Tracey
Keyword(s):  
Tensile Strength ◽  
Silicon Nitride ◽  
Process Control ◽  
High Reliability ◽  
Heat Engine ◽  
High Strength ◽  
Processing Unit ◽  
Unit Operations ◽  
Engine Components ◽  
Strength Database

The paper discusses highlights of a silicon nitride processing methodology that has been developed in the course of a major four year DoE funded program in processing for reliability. The program focused on the attainment of high strength and reliability through the identification and subsequent control of strength degrading flaws introduced during processing unit operations. Process control and NDE methods applied to achieve an optimized process with the potential to produce high reliability advanced heat engine components are discussed. Concluding remarks are directed to the extensive tensile strength database that has been generated through testing of over 300 tensile rods produced by the optimized process.

scholarly journals Development of Improved Processing and Evaluation of Silicon Nitride

1991 ◽  
Author(s):  
V. K. Pujari ◽  
K. E. Amin ◽  
P. H. Tewari
Keyword(s):  
Tensile Strength ◽  
Silicon Nitride ◽  
Injection Molding ◽  
Nondestructive Evaluation ◽  
High Reliability ◽  
Rupture Life ◽  
Heat Engine ◽  
Stress Rupture ◽  
Stress Rupture Life ◽  
Process Route

The goals of this program are to develop and demonstrate significant improvements in processing methods, process controls, and nondestructive evaluation (NDE) which can be commercially implemented to produce high-reliability silicon nitride components for advanced heat engine applications at temperatures to 1370°C. Achievement of this goal is being sought by • The use of silicon nitride - 4% yttria composition which is consolidated by glass encapsulated HIP’ping. • The generation of baseline tensile strength data from an initial process route involving injection molding. • Fabrication of tensile test bars by colloidal techniques, e.g. injection molding and colloidal consolidation. • Identification of (critical) flaw populations through NDE and fractographic analysis of tensile bars. • Correlation of measured tensile strength with flaw populations and process parameters. • Minimization of these flaws through innovative improvements in process methods and controls. The program goals are: • mean room temperature tensile strength of 900 MPa and Weibull modulus of 20; • mean 1370°C fast fracture tensile strength of 500 MPa; • mean 1230°C tensile stress rupture life of 100 hours at 350 MPa. This report describes the progress made to date in developing injection molding and colloidal consolidation processes for the net shape forming (NSF) of tensile bars, nondestructive evaluation of processed material, and tensile testing of net shape bars in green and densified states.

A Cost Effective Process for Silicon Nitride Engine Components

1994 ◽  
Author(s):  
Garry J. Garvey ◽  
Jack D. Sibold
Keyword(s):  
Silicon Nitride ◽  
High Reliability ◽  
Low Cost ◽  
High Strength ◽  
Cost Effective ◽  
Shock Resistance ◽  
Baseline Cost ◽  
Engine Components ◽  
Low Cost Manufacturing ◽  
High Thermal Shock Resistance

Silicon Nitride (Si3N4) ceramics offer tremendous material advantages for automotive and other high strength, high thermal shock resistance applications. Yet while the need for such a material continues to rise, the high cost of silicon nitride components remains a significant barrier to market acceptance. It was determined that market acceptance hinged on achieving three goals: high flexural strength (i.e. 4 pt. MOR >525 MPa), high reliability (i.e. Weibull modulus >15) and a spray-dried body cost of <$13.00/kg. To address this need, GTC/Coors licensed a prototype process from Eaton for making Sintered Reaction-Bonded Silicon Nitride (SRBSN) that offered the potential for low cost manufacturing. This paper describes the process optimization that took place to adapt this prototype process to GTC/Coors existing manufacturing technology base. It also presents the material properties and baseline cost-efficiency goals that were achieved.

Thermal and Loading Effects on Mechanical Properties of a Hot Isostatically Pressed Si3N4

1994 ◽  
Author(s):  
Jagannathan Sankar ◽  
Jayant Neogi ◽  
Suneeta S. Neogi ◽  
Marvln T. Dixie ◽  
Ranji Vaidyanathan
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Silicon Nitride ◽  
Elevated Temperatures ◽  
Heat Engine ◽  
Tensile Tests ◽  
Tensile Creep ◽  
Uniaxial Tensile ◽  
Creep Tests ◽  
Loading Effects

The effect of thermal soaking on the mechanical properties of a candidate material for advanced heat engine applications namely, hot isostatically pressed (HIPed) silicon nitride (GTEPY6) are reported here. Pure uniaxial tensile tests conducted at room and at elevated temperatures indicated that the tensile strength of this material dropped significantly after 1000°C. The residual tensile strength of PY6 material after thermal soaking at 1200° and 1300°C was also investigated. Test results showed that thermal soaking at 1200° and 1300°C increased the residual tensile strength. The thermal soaking time had a greater effect on the residual tensile strength at 1300°C. Tensile creep tests performed at 1200° and 1300°C showed that the steady state creep rate was influenced by both the temperature and the applied stress. The higher stress exponent in HIPed as compared to a sintered silicon nitride shows higher creep resistance in the case of HIPed materials.

GTE Sintered Silicon Nitride

1984 ◽  
Author(s):  
C. L. Quackenbush ◽  
J. T. Smith
Keyword(s):  
Silicon Nitride ◽  
Weibull Modulus ◽  
Heat Engine ◽  
Future Directions ◽  
Heat Engines ◽  
The Status ◽  
Density Surface ◽  
Microstructure Density ◽  
Engine Components ◽  
Sintered Silicon

A status of GTE sintered silicon nitride for advanced heat engines will be presented. This will include an update of: sintering and final properties for a number of GTE silicon nitride compositions, microstructure, density, surface finish, strength, Weibull modulus, oxidation resistance, fracture toughness etc. The status of heat engine components fabricated by injection molding or isopressed/green machining and their performance will be reviewed along with correlations between the shape fabrication technique, strength, and Weibull modulus. Costs and availability will be included where possible. Future directions for increased reliability in silicon nitride structural ceramics will be summarized.

scholarly journals Development of Silicon Nitride Engine Components for Advanced Gas Turbine Applications

1990 ◽  
Author(s):  
B. J. Busovne ◽  
J. P. Pollinger
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
High Strength ◽  
Current Status ◽  
Statistical Process ◽  
Technology Applications ◽  
Ceramic Components ◽  
Net Shape Forming ◽  
Engine Components

The development and fabrication of reliable high temperature-high strength silicon nitride rotors by Garrett Ceramic Components for the Advanced Turbine Technology Applications Project (ATTAP) is discussed. The current status of rotor net-shape forming capability, achievable mechanical properties, NDE development/implementation, and statistical process control results will be presented.

scholarly journals Improved Processing Methods for Silicon Nitride Ceramics

1991 ◽  
Author(s):  
S. Natansohn ◽  
A. E. Pasto
Keyword(s):  
Tensile Strength ◽  
Silicon Nitride ◽  
Powder Processing ◽  
Hot Isostatic Pressing ◽  
High Strength ◽  
Complete Characterization ◽  
Nitride Ceramics ◽  
The Status ◽  
Powder Characteristics ◽  
Non Destructive

This paper reviews the status of a program1 to develop silicon nitride ceramics of high strength and reliability, with the material performance goals being a tensile strength of 900 MPa at room temperature and 500 MPa at 1370°C, both with a Weibull modulus of 20. The selected process consists of injection molding and hot isostatic pressing of a silicon nitride formulation containing 6 w/o yttria as sintering aid. A comprehensive experimental approach has been adopted which consists of: a. complete characterization and subsequent modification of the starting silicon nitride powder in an attempt to correlate powder characteristics to ceramic properties; b. the design and fabrication of appropriate specimens for tensile strength testing; c. the implementation of alternate powder processing and shaping techniques, including the design of new compounding/molding equipment; and d. the expansion of non-destructive evaluation capabilities.

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