Method of surface-treating ceramic workpieces using a laser

Claim 1

A method of surface treating ceramic workpieces by means of a laser, the method being applicable to a workpiece to be treated constituted by a base ceramic material including surface cracks and/or pores, the method including the steps of: scanning at least a portion of the surface of the workpiece to be treated with a heating laser beam in order to provide a melt zone in which the temperature is locally raised above the melting temperature of the material, in such a manner that, at each point of the treated surface, the melting and subsequent cooling of a surface layer give rise to a microstructure in said layer which is finer and/or more homogeneous than before; and projecting a ceramic powder onto the workpiece to be treated in the heating laser beam, in such a manner that the projected powder arrives in the melted state in said melt zone, with the throughput of said powder being chosen to be high enough to add on a sufficient quantity of ceramic material to fill at least 50% by volume of the initial surface cracks and pores in the base material when in the solid state, thereby at least partially avoiding the formation of shrinkage microcracks on cooling, and said throughput also being chosen simultaneously to be small enough for the heating power absorbed by the melting of said powder to be less than the heating power absorbed by melting the molten surface layer of said base material, thereby ensuring that said molten powder is integrated homogeneously in the base material.

Claim 2

A method of surface treating ceramic workpieces by means of a laser, the method being applicable to a workpiece to be treated constituted by a base ceramic material including surface cracks and/or pores, the method including the steps of: scanning at least a portion of the surface of the workpiece to be treated with a heating laser beam in order to provide a melt zone in which the temperature is locally raised above the melting temperature of the material, in such a manner that, at each point of the treated surface, the melting and subsequent cooling of a surface layer give rise to a microstructure in said layer which is finer and/or more homogeneous than before; and projecting a ceramic powder onto the workpiece to be treated in the heating laser beam, in such a manner that the projected powder arrives in the melted state in said melt zone, with the throughput of said powder being chosen to be high enough to add on a sufficient quantity of ceramic material to fill at least 50% by volume of the initial surface cracks and pores in the base material when in the solid state, thereby at least partially avoiding the formation of shrinkage microcracks on cooling, and said throughput also being chosen simultaneously to be small enough for the heating power absorbed by the melting of said powder to be less than the heating power absorbed by melting the molten surface layer of said base material, thereby ensuring that said molten powder is integrated homogeneously in the base material.