Molten salt corrosion of hot-pressed Si sub 3 N sub 4 /SiC-reinforced composites and effects of molten salt exposure on slow crack growth of hot-pressed Si sub 3 N sub 4

Conference · Fri Nov 03 00:00:00 EST 1989

OSTI ID:7152329

Henager, Jr, C H; Jones, R H

Corrosion and slow crack growth of hot-pressed Si{sub 3}N{sub 4}- based ceramic materials were studied to arrive at an initial determination of the severity of Na{sub 2}SO{sub 4} molten salt environments. Slow crack growth testing revealed that Na{sub 2}SO{sub 4} molten salt exposure accelerated crack growth in hot-pressed Si{sub 3}N{sub 4} compared to crack growth in air at 1300 C. The salt exposure was observed to reduce the time to failure of precracked specimens by factors of two or three. Measured crack velocity was observed to obey a power law, V = AK{sup n}, with n = 5.2 {plus minus} 0.2 and A = 7.6 {times} 10{sup {minus}10}. Standard corrosion coupon tests were performed on specimens of Si{sub 3}N{sub 4}/SiC-reinforced composites and hot-pressed Si{sub 3}N{sub 4} monolithic material. Weight change measurements were performed after eight-hour immersion exposures at 950, 975, and 1000 C to Na{sub 2}SO{sub 4}. Hot-pressed Si{sub 3}N{sub 4} + 5% MgO and Si{sub 3}N{sub 4}/SiC whisker-reinforced material exhibited similar surface features after molten salt exposure. A Si{sub 3}N{sub 4}/SiC fiber-reinforced material, however, revealed complete dissolution of SiC chopped fiber reinforcements.

• Research Organization: Pacific Northwest Lab., Richland, WA (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 7152329
• Report Number(s): PNL-SA-17162; CONF-8910120-9; ON: DE90008624
• Resource Relation: Conference: 1. international ceramic science and technology congress, Anaheim, CA (USA), 31 Oct - 3 Nov 1989
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
SILICON NITRIDES
CORROSION
SODIUM SULFATES
CORROSIVE EFFECTS
CERAMICS
COMPOSITE MATERIALS
CRACK PROPAGATION
FIBERS
HOT PRESSING
MAGNESIUM OXIDES
SALTS
SILICON CARBIDES
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CARBIDES
CARBON COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
FABRICATION
MAGNESIUM COMPOUNDS
MATERIALS
MATERIALS WORKING
NITRIDES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PNICTIDES
PRESSING
SILICON COMPOUNDS
SODIUM COMPOUNDS
SULFATES
SULFUR COMPOUNDS
360205* - Ceramics
Cermets
& Refractories- Corrosion & Erosion
360203 - Ceramics
Cermets
& Refractories- Mechanical Properties