Sermatech International Inc.

Purusottam Sahoo

Stephen G Sitko

Anthony Mallilo

A strain tolerant ceramic coating, preferably for use as an abrasive coating on a substrate is provided. The coating is prepared from a yttria and zirconia powder having an average particle size less than 40 microns. The coating is formed by depositing the powder on the substrate by a plasma spray process. The as-applied coating contains essentially no macrocracks, but a post-stressed coating contains a random distribution, population, and orientation of microcracks and macrocracks.

Strain tolerant ceramic coating

Known thermal spray apparatus are modified to achieve thermal spray coatings of increased hardness. Thermal spray apparatus operate to develop a plasma stream for introduction to a nozzle, for eventual application to the surface of a substrate. Upon entering the nozzle, the plasma stream is passed through a plasma cooling zone defined by a plasma cooling passageway, to a plasma accelerating zone defined by a narrowed passageway that expands into a plasma/particle confining zone for the discharge of material from the apparatus. The narrowed passageway of the apparatus is cooled, and the powder material to be applied by the apparatus is introduced into the plasma stream along the cooled, narrowed passageway. To apply thermal spray coatings of increased hardness to a substrate, the ratio of the length of the plasma/particle confining zone relative to the diameter of the plasma/particle confining zone (the 'L/D' ratio) is increased from the more conventional value of about 5:1, preferably to a ratio in a range of from 7:1 to 16.5:1, for use with coating materials including WC--Co, Cr.sub.3 C.sub.2 --NiCr and Cr.sub.3 C.sub.2. Ratios of from 10:1 to 13:1 have been found to achieve a particularly desirable result. Also the method and the coatings obtained.

Method and apparatus for applying coatings using a nozzle assembly

Known thermal spray apparatus are modified to achieve rough thermal spray coatings. Thermal spray apparatus operate to develop a plasma stream for introduction to a nozzle, for eventual application to the surface of a substrate. Upon entering the nozzle, the plasma stream is passed through a plasma cooling zone defined by a plasma cooling passageway, to a plasma accelerating zone defined by a narrowed passageway that expands into a plasma/particle confining zone for the discharge of material from the apparatus. The narrowed passageway of the apparatus is cooled, and the powder material to be applied by the apparatus is introduced into the plasma stream along the cooled, narrowed passageway. For the appropriate heating (melting) and acceleration of MCrAlY powder particles, for application to the substrate which is to receive the thermal spray coating, the ratio of the cross-sectional area of the initial (plasma cooling) passageway relative to the cross-sectional area of the narrowed (plasma accelerating) passageway is reduced from the more conventional value of about 4:1 to a ratio of 2:1 or less.

Thermal spray nozzle method for producing rough thermal spray coatings

A method for applying a thermal spray coating onto a substrate (24) includes the steps of providing chamber apparatus (10) including a chamber (16) having a gas flow assembly (23) that includes a gas injector (27) and a spray nozzle (30) therein for introducing, a gas and spray coating. The chamber has an adjustably sized restricted opening (18) that is continuously open to the ambient atmosphere (21) that is exterior of the chamber (16). The total gas flow is maintained from the gas flow assembly (23) at a predetermined rate based on the size of the restricted opening (18) and the amount of oxygen that is desired to be present during the spraying of the coating and thereafter until the spray coating solidifies on the substrate. Gas flow from the spray nozzle (30) is determined by optimum process parameters for coating specified materials. If the gas flow from the nozzle (30) is insufficient to provide the total gas flow, the gas injector (27) supplements the total gas flow.

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Collegeville, PA, United States of America

Purusottam Sahoo