# Presentation: 143319

** ****Hot Section Silicon Nitride**
**Materials Development For**
**Advanced Microturbines**
**Applications**

*9 Goddard Road*
*Northboro, MA 01532*

**EBC Workshop**
***November 18, 2003***
***Nashville, TN***
***Vimal Pujari, Ara Vartabedian,***
***Bill Collins, James Garrett***
***Saint-Gobain Ceramics & Plastics, Inc.***

- © 2003 Saint-Gobain Ceramics & Plastics, Inc.

## Hot Section Materials Development For Advanced Microturbines Program

- Co-Authors:  Bill Collins, Bill Donahue, James Garrett, Oh-Hun Kwon, Bob Licht, Vimal Pujari, Ara Vartabedian
**Acknowledgements**
- Research sponsored by U.S. Department of Energy (DOE), Energy Efficiency & Renewable Energy, and Oak Ridge National Laboratory (ORNL) managed by UT- Battelle, LLC, under Prime Contract No. DE-AC05-00OR22725 with the DOE.
- ORNL -- Dave Stinton, Terry Tiegs, Matt Ferber, Peter Tortorelli, Shannon Bridges.
- DOE -- Debbie Haught, Steve Waslo, Jill Jonkowski
- UTRC -- John Holowczak, Gary Linsey, Bill Treadway
- Dave Richerson, Dave Carruthers

## Objective

**Hot Section Si****3****N****4**** for Advanced Microturbine Program**
- Under DOE/ORNL Program, Develop and improve a cost-effective, reliable monolithic silicon nitride material for Hot Section Components in DER Advanced Microturbine Systems
- Through surface engineering, demonstrate sufficient environmental stability for operation w/o EBC -- Or compatible with EBC

## Hot Section Materials Development For Advanced Turbines (Phase I)

- Net Shape
- Comp.
- Prop.

- Failure
- Prob.
- Analysis

- Redefine
- Prop.
- Goals

- Prop. Impr.
- Plan &
- Implmenta-
- tion

- Material
- Selection
- From
- Design
- Envelop

- NT154

- Large
- X-Sect.
- Comp.

- HIP

- Closed
- Loop
- Process’g
- (CLP)

- -
- SiAlon

- NT154

- CIP
- Specimen

- GPS

- Test
- Specimen
- Properties

- CIP
- Specimen

- HIP

- Test
- Specimen
- Properties

**TASK 3**

**TASK 2**

**TASK 1**

## Material and Process Approach

**Ceramic Microturbine Technology**

**Material **
**Development**

** ****Re-establish NT154**
** ****Improve NT154**
** ****Recession Control**
** ****Alternate Composition**

**Net Shape Forming **
**Development**

** ****Green CNC Machining**
** ****Casting / Molding**

## Testing at ORNL

**NT154 Material Qualification**

**Delivered task I tiles**
- Testing has been completed
**Delivered task II tiles**
- Optimized HIP conditions for bulk material
- Two sets of tiles
- Room temperature fast fracture testing completed

## Room Temperature Fast Fracture Results

**Need to improve as-processed (AP) properties**

_**Bulk**_
**********=929 MPa**
**m=21.4**

_**AP**_
**********=574 MPa**
**m=4.7**

**Testing at ORNL**

**NT154 Task I**

## Testing at ORNL

**NT154 Task I**

**Fast fracture material properties re-established**

## Testing at ORNL

**Testing at ORNL**

**NT154 Task I**

## Testing at ORNL

**Fatigue exponents similar to historical data**

**Testing at ORNL**

**NT154 Task I**

## Testing at ORNL

**Testing at ORNL**

**NT154 Task I**

## Testing at ORNL

**Continued need to improve as-processed (AP) properties**

**Testing at ORNL**

**NT154 Data**

## High Temperature Strength

**Mechanical Properties (Bulk Material)**

**Influence of Binder Level on Properties**

## As-Processed Surface

**Looking to reduce the Si3N4 interaction with the HIP glass**
- Influence on the near surface material
**Initial experiments done in a laboratory scale HIP**
**Etched microstructure of the near surface material**

**Proprietary New HIP Process**

## As-Processed Surface

**As-Processed Surface**

**Proprietary New HIP Process**

## As-Processed Surface

**As-Processed Surface**

**Proprietary New HIP Process**

## As-Processed Surface

- Important for net-shape turbine components

**50% improvement in AP strength!**

**As-Processed Surface**

**Proprietary New HIP Process**

## As-Processed Surface

**New HIP process minimizes interaction with the HIP glass**
**In process of scaling up new process to production HIP**
- Initial experiments result in a decrease in AP properties for both the old and new processes
- The new process still provides up to a 50% improvement compared to the old process
- Issue appears to be with the near surface microstructure

**As-Processed Surface**

**Conclusions**

## Developed green-machining process
Completed two demonstration axial rotors
Green dimensions within 0.003” of nominal
Dense surface roughness
Hub:  35-40 in
Blades:  55-75 in
Uniform/isotropic shrinkage
High yield
Flexible prototyping process

**Completed two demonstration axial rotors**
**Green dimensions within 0.003” of nominal**
**Dense surface roughness**
- Hub:  35-40 in
- Blades:  55-75 in
**Uniform/isotropic shrinkage**
**High yield**
**Flexible prototyping process**

**Net Shape Forming**

**Green Machining**

## Net Shape Forming

**Machining completed on four prototypes**
- Machining time reduced by ~20%

**Net Shape Forming**

**Green Machining**

## Net Shape Forming

- Blades:  25 in
- Bottom face:  30 in
**CMM on green rotors**
- Dimensions within 0.004” of nominal
- Concentricity within 0.002”
- Blade surface locations within 0.003”
**Rotors to be HIPed**
- Use new process for improved AP
- Shrinkage uniformity
- Surface roughness change
- CMM
**Material property evaluation at ORNL**
**Test in Ingersoll-Rand microturbine?**

**Net Shape Forming**

**Green Machining**

## Net Shape Forming

**Direct Starch Casting**

**Objective**
- 	Develop a complex shape forming method using 	highly loaded starch containing ceramic suspension
**Optimization**
- Improve density and minimize internal porosity
- Increase green strength
- Improve surface finish

## Net Shape Forming

**DIRECT STARCH CASTING (UNDRAINED)**
**           ****NO DRYING SHRINKAGE**

**SLIP CASTING (DRAINED)**
**      ****DRYING SHRINKAGE**

**POROUS MOLD**
**ROOM T****EMPERATURE**

**NON POROUS MOLD**
** ****T= 60****°C**

**WATER MIGRATION**
**STARCH PARTICLE**

**Net Shape Forming**

**Direct Starch Casting**

## Net Shape Forming

**Improvements seen with standard starch compared to past results**
**Further improvements seen with Starch B**
- However, shrinkage is present
**Surface roughness improvement demonstrated using new AP process**
- 34% decrease for standard starch (not shown in table)
**Further work would study the casting of complex shapes**

**Net Shape Forming**

**Direct Starch Casting**

## Recession Control

- Baseline NT154 samples (uncoated) being tested
- Preliminary test conditions
- 1200oC
- 3% or 20% H2O
- 10atm total pressure, 1.5atm water vapor pressure
- Up to 2500 hours
**Initial HEEPS coating analyzed**
- In-situ process to modify surface during HIP
- Y2SiO5 dip-coat
- Occasional cracking is evident by optical microscope
- Spot XRD suggests Y2SiO5 layer no longer exists
**Initial Ceramatec coatings analyzed**
- Proprietary coatings on dense NT154 tiles
- Cracks are evident by SEM
- Further process improvement necessary

**Recession Control**

## Conclusions

**Improvements in high temperature strength**
**Improved AP strength through new HIP process**
- Need to reproduce results in production HIP
**Prototyping of microturbine rotors through green machining**
**Improvements seen in starch casting**
- Properties comparable to baseline NT154
**Key microturbine OEM’s contacted**
**Three invention disclosures filed**

**Conclusions**

## Microturbine Plan For FY2004

- ORNL program continuation to develop an innovative protective layer
- “HEEPS” *(In situ)* and EBC approaches
**Continue Material and Forming Advancements**
- Continue to evaluate AP properties
- Continue to evaluate green-machining approach
- Direct casting improvements
**Prototypes in Support of OEMs**
- Mechanical testing of a component at ORNL
- Plans to work with Microturbine manufacturers
- Cost analysis

**Microturbine Plan For FY2004**