Patent GB-967952-A (GB)
Title: High temperature flame spraying of ceramic material
Inventor: HUFFADINE JOHN BERTRAM
Filed: 1959-12-11
Abstract: A method of producing a refractory alumina body by projecting on to a base or former alumina material in a particulate or droplet form (as in Specification 903,709), is characterized in that the projection is at such a temperature (exceeding 1200 DEG  C.) that the alumina is deposited in the alpha form.  In one method a stainless steel wire mesh former mounted on a rotatable support is first coated with a thin layer of gamma alumina by means of a flame spray gun, after which the subsequent layers necessary to form the required thickness are deposited by a high temperature flame; during the building up of the alpha alumina layers the original gamma layer is transformed to alpha.  After the deposition the wire mesh is removed from the ceramic body by grit-blasting or by dissolution.  If desired the refractory body can be reinforced either by a fibrous dispersed phase or by a wire as in Specification 953,651.  In an alternative method the base is a water-cooled metal former over which is stretched a woven or knitted layer of silica fibres.  The formed body can be readily removed both from the metal former and from the woven or knitted layer, and the latter can be re-used several times.  If a single flame spray gun is used for the deposition it is moved axially relative to the former whilst the former is rotating, the speeds of axial movement and rotation being such that the wall of the body is built up to the required thickness in a single pass of the spraying gun.  The former may rotate about a horizontal or a vertical axis, a vertical axis being preferred when making large refractory bodies.ALSO:A method of producing a refractory alumina body by projecting on to a base or former alumina material in a particulate or droplet form (as in Specification 903,709), is characterized in that the projection is at such a temperature (exceeding 1200  DEG C.) that the alumina is deposited in the alpha form.  In one method a stainless steel wire mesh former mounted on a rotatable support is first coated with a thin layer of gamma alumina by means of a flame spray gun, after which the subsequent layers necessary to form the required thickness are deposited by a high temperature flame; during the building up of the alpha alumina layers the original gamma layer is transformed to alpha.  After the deposition the wire mesh is removed from the ceramic body by grit-blasting or by dissolution.  If desired the refractory body can be reinforced either by a fibrous dispersed phase or by a wire as in Specification 953,651.  In an alternative method the base is a water-cooled metal former over which is stretched a woven or knitted layer of silica fibres.  The formed body can be readily removed both from the metal former and from the woven or knitted layer, and the latter can be re-used several times. If a single flame spray gun is used for the deposition it is moved axially relative to the former whilst the former is rotating, the speeds of axial movement and rotation being such that the wall of the body is built up to the required thickness in a single pass of the spraying gun.  The former may rotate about a horizontal or a vertical axis, a vertical axis being preferred when making large refractory bodies.