Abstract: The Cr.sub.2 O.sub.3 protective coating (3) is applied, during the vacuum spray process, as a leakproof coating to a support (1), and has a density of not more than 5.3 g/cm.sup.3, a residual porosity of less than 2%, a Vickers hardness (HV) of over 2000 kp/mmm.sup.2 and an electric strength of at least 5 V/.mu.m of protective thickness; it is particularly suited as a protective coating on supports (3) exposed to corrosion and simultaneously subjected to high mechanical loads.

Abstract: The protection layer (3,4,5) applied to a support (1) by a vacuum plasma spraying process comprises an adherence layer (3), an intermediate layer (4) and a coating layer (5). In order to enable a universal application of the protection, particularly in the construction of turbines, foundry and nuclear technique, the adherence layer (3) is made of a selected material having a composition and a thermal expansion coefficient close to those of the material of the object to be coated (1). The intermediate layer (4) is comprised of a mixture of the material of the adherence layer (3) and of that of the coating layer (5) and the coating layer is comprised of a thick layer of sprayed material selected in the group of borides, carbides, nitrides and oxides of preferably TiB.sub.2 or Al.sub.2 O.sub.3.

Abstract: In a plasma spray gun (1) including a cooled electrode (10) and burner nozzle (12) for insertion in pipes and bores of work pieces and for coating the inner surfaces of these work pieces, for the coating of bores with a minimal diameter of 25 mm the electrode (10) is designed rotation-asymmetrically in the area of its head (15), and the diameter of the electrode (10) is smaller than the minimal inner diameter of the burner nozzle (12), while the burner nozzle (12) on the end facing away from the electrode (10) has at least one partial area (17) with an inner diameter which is larger than its minimal inner diameter, and the powder injector (13) has a flat exit cross-section.

Abstract: A vacuum plasma coating apparatus comprises a plasma torch arranged in a low pressure chamber and displaceable along a plurality of axes relative to the part to be coated and a device for moving the part to be coated with a plurality of degrees of freedom simultaneously with the plasma torch. In order to be able to coat a plurality of parts simultaneously with great effectiveness, a device for moving the part to be coated is constructed in such manner that it can contain a plurality of parts simultaneously, the parts being movable simultaneously and/or sequentially through the plasma jet. In each case the part nearest the plasma torch is arranged in the plasma jet in such manner that this extends at least occasionally laterally beyond an outer dimension of this part and all parts to be coated move within a predetermined spray distance range when they are located in the plasma jet.

Abstract: Powder is fed from a container into a continuous annular groove on a rotating metering plate. A doctor member ensures that the powder is correctly filled into the groove. The powder is then sucked out of the groove after the plate has rotated through a certain angle by a suction device which has a projection extending into the groove.

Abstract: Plasma spraying apparatus is provided with means for selective release of carrier gas for the coating powder prior to the injection of the powder into the plasma stream. The gas release is effected by one or two apertured tube wall portions associated with a closure sleeve slidable on the tube or by a swirl chamber with a lateral gas outlet provided with a filter and a regulating valve.