Environmental Effects on the Time Dependent Failure of Non-Oxide Ceramics

Abstract

The mechanical and chemical factors that contribute to time dependent strength changes have been investigated for a variety of non-oxide materials including silicon nitride, silicon carbide and siliconized silicon carbide. The flaw behavior in an as-machined and oxidized HIP'ed silicon nitride under static load was investigated at various stress intensities, times, and temperatures. Flaw origins were of the pore/cavity and iron-based inclusion type. There was no strength increase or degradation in as-machined and oxidized samples static loaded for ten hours at 1100 C in air below the threshold stress intensity. The threshold stress intensity for crack growth at 1100 C were determined to be 1.75 and 2.00 MPa.m1/2 for the as-machined and oxidized HIPSN, respectively. A strength decrease with increased applied stress was observed in as-machined specimens static loaded at 1200 C and 1300 C in air. This effect is due to the creation of a new flaw population with more severe flaws. Keywords: Silicon nitride, Silicon carbide, Oxidation, High temperature strength, Threshold stress intensity, Slow crack growth, Tensile creep behavior, Cavitation, Creep damage.

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Document Details

Document Type
Technical Report
Publication Date
Nov 03, 1988
Accession Number
ADA202391

Entities

People

  • Richard E. Tressler

Organizations

  • University of Pennsylvania

Tags

Communities of Interest

  • Advanced Electronics

DTIC Thesaurus Topics

  • Ceramic Materials
  • Chemical Reactions
  • Chemistry
  • Creep
  • Crystal Structure
  • Engineered Materials
  • Material Degradation Processes
  • Materials
  • Materials Laboratories
  • Materials Processing
  • Materials Science
  • Materials Testing
  • Mechanical Properties
  • Mechanical Working
  • Mechanics
  • Silicon Carbide
  • Transition Temperature

Readers

  • Materials Science (Mechanical Engineering).
  • Powder metallurgy of Titanium alloys.