Production of high strength carbide fibers by heat treatment

Claim 2

A process for strengthening a curled carbide-containing fiber, said fiber comprising a material selected from the group consisting of carbides of boron, chromium, molybdenum, hafnium, zirconium, tantalum, niobium, and mixtures thereof, comprising the steps of: 1. heating, at a temperature in the range of about 2050°C to about 2300°C, for a period of about 0.2 to about 10 minutes, the curled carbide-containing fiber while, simultaneously, 2. subjecting the curled carbide-containing fiber to tensile stress in the range of about 200 to about 3500 psi to essentially remove internal fiber stresses, straighten the fiber and thereby increase the tensile strength of the carbide-containing fiber.

Claim 3

A process according to claim 1 in which the curled carbide-containing fiber has a diameter ranging from about 8 to about 14 microns.

Claim 4

A process according to claim 1 in which the curled carbide contained in the carbide-containing fiber is boron carbide.

Claim 5

A process according to claim 3 in which the curled carbide-containing fiber has a diameter of about 8 to about 9 microns and the heating is in the range of about 2100° to about 2200°C, said fiber being under a tensile stress ranging from about 2000 to about 3000 p.s.i. for a time period of about 0.5 to about 1.5 minutes.

Claim 6

An improved process for increasing the tensile strength of a carbide-containing fiber, said fiber comprising a material selected from the group consisting of carbides of boron, chromium, molybdenum, hafnium, zirconium, tantalum, niobium, and mixtures thereof, in which said carbide-containing fiber is first simultaneously heated and exposed to the vapor of a halide of a carbide forming element to form a curled carbide-containing fiber; wherein the improvement comprises a second heating, at a temperature in the range of about 2050°C to about 2300°C, for a period of about 0.2 to about 10 minutes, of the curled carbide-containing fiber while simultaneously subjecting the curled carbide-containing fiber to tensile stress to essentially remove internal fiber stresses, straighten said fiber, and thereby increase the tensile strength of the carbide containing fiber.

Claim 7

An improved process for increasing the tensile strength of a carbide-containing fiber, said fiber comprising a material selected from the group consisting of carbides of boron, chromium, molybdenum, hafnium, zirconium, tantalum, niobium, and mixtures thereof, in which said carbide-containing fiber is first simultaneously heated and exposed to the vapor of a halide of a carbide forming element to form a curled carbide-containing fiber; wherein the improvement comprises a second heating, at a temperature in the range of about 2050°C to about 2300°C, for a period of about 0.2 to about 10 minutes, of the curled carbide-containing fiber while simultaneously subjecting the curled carbide-containing fiber to tensile stress to essentially remove internal fiber stresses, straighten said fiber, and thereby increase the tensile strength of the carbide containing fiber.