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Title: Superplastic forging nitride ceramics

Abstract

A process is disclosed for preparing silicon nitride ceramic parts which are relatively flaw free and which need little or no machining, said process comprising the steps of: (a) preparing a starting powder by wet or dry mixing ingredients comprising by weight from about 70% to about 99% silicon nitride, from about 1% to about 30% of liquid phase forming additive and from 1% to about 7% free silicon; (b) cold pressing to obtain a preform of green density ranging from about 30% to about 75% of theoretical density; (c) sintering at atmospheric pressure in a nitrogen atmosphere at a temperature ranging from about 1,400 C to about 2,200 C to obtain a density which ranges from about 50% to about 100% of theoretical density and which is higher than said preform green density, and (d) press forging workpiece resulting from step (c) by isothermally uniaxially pressing said workpiece in an open die without initial contact between said workpiece and die wall perpendicular to the direction of pressing and so that pressed workpiece does not contact die wall perpendicular to the direction of pressing, to substantially final shape in a nitrogen atmosphere utilizing a temperature within the range of frommore » about 1,400 C to essentially 1,750 C and strain rate within the range of about 10[sup [minus]7] to about 10[sup [minus]1] seconds[sup [minus]1], the temperature and strain rate being such that surface cracks do not occur, said pressing being carried out to obtain a shear deformation greater than 30% whereby superplastic forging is effected.« less

Inventors:
; ;
Publication Date:
Research Org.:
Jupiter Technologies
OSTI Identifier:
7072573
Patent Number(s):
US 4732719; A
Application Number:
CNN: SB1R 1985-10; PPN: US 6-816040
Assignee:
Jupiter Technologies, Inc., Ithaca, NY (United States)
DOE Contract Number:  
AC01-84ER80167
Resource Type:
Patent
Resource Relation:
Patent File Date: 3 Jan 1986
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; SILICON NITRIDES; FORGING; COLD WORKING; CONTROLLED ATMOSPHERES; PLASTICITY; SINTERING; TEMPERATURE DEPENDENCE; ATMOSPHERES; FABRICATION; MATERIALS WORKING; MECHANICAL PROPERTIES; NITRIDES; NITROGEN COMPOUNDS; PNICTIDES; SILICON COMPOUNDS; 360201* - Ceramics, Cermets, & Refractories- Preparation & Fabrication

Citation Formats

Panda, P C, Seydel, E R, and Raj, R. Superplastic forging nitride ceramics. United States: N. p., 1988. Web.
Panda, P C, Seydel, E R, & Raj, R. Superplastic forging nitride ceramics. United States.
Panda, P C, Seydel, E R, and Raj, R. Tue . "Superplastic forging nitride ceramics". United States.
@article{osti_7072573,
title = {Superplastic forging nitride ceramics},
author = {Panda, P C and Seydel, E R and Raj, R},
abstractNote = {A process is disclosed for preparing silicon nitride ceramic parts which are relatively flaw free and which need little or no machining, said process comprising the steps of: (a) preparing a starting powder by wet or dry mixing ingredients comprising by weight from about 70% to about 99% silicon nitride, from about 1% to about 30% of liquid phase forming additive and from 1% to about 7% free silicon; (b) cold pressing to obtain a preform of green density ranging from about 30% to about 75% of theoretical density; (c) sintering at atmospheric pressure in a nitrogen atmosphere at a temperature ranging from about 1,400 C to about 2,200 C to obtain a density which ranges from about 50% to about 100% of theoretical density and which is higher than said preform green density, and (d) press forging workpiece resulting from step (c) by isothermally uniaxially pressing said workpiece in an open die without initial contact between said workpiece and die wall perpendicular to the direction of pressing and so that pressed workpiece does not contact die wall perpendicular to the direction of pressing, to substantially final shape in a nitrogen atmosphere utilizing a temperature within the range of from about 1,400 C to essentially 1,750 C and strain rate within the range of about 10[sup [minus]7] to about 10[sup [minus]1] seconds[sup [minus]1], the temperature and strain rate being such that surface cracks do not occur, said pressing being carried out to obtain a shear deformation greater than 30% whereby superplastic forging is effected.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1988},
month = {3}
}