Process for the manufacture of substantially pore-free shaped polycrystalline articles by isostatic hot-pressing

US4351858A · kind A · utility

Assignee

• Elektroschmelzwerk Kempten GmbH · DE

Inventors

• Klaus Hunold · Kempten, DE
• Klaus Reinmuth · Durach, DE
• Alfred Lipp · Bad Wörishofen, DE
• Johannes Napholcz · Kempten, DE
• Peter Arnold · Earby, GB

Key dates

• Filing date: Feb 25, 1981
• Grant date: Sep 28, 1982
• Expiry date: Feb 25, 2001

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B22F2998/00
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

The invention is a process for the manufacture of substantially pore-free shaped articles from polycrystalline material, such as tungsten carbide, silicon nitride, titanium boride or silicon carbide, in which encased articles preformed from pulverulent materials and having open pores are isostatically hot-pressed in a vacuum-sealed casing of vitreous or ceramic-like material in a high-pressure autoclave using an inert gas as pressure-transfer medium. Before the application of the casing material, a first layer comprising material that can be decomposed or melted, such as an organic wax or a resin-like product, or of a compressible heat-resistant material such as inorganic fibers or felts, is applied to the preformed articles. Then, the encased articles are thermally treated until the glass or ceramic layer is fused or sintered gas-tight. The articles pretreated in this manner are then isostatically hot-pressed.