SOME TECHNIQUES FOR REDUCING FILLER POWDER LOSSES IN MICROPLASMA CLADDING

摘要

At reconditioning of the edges of gas turbine engine blades by microplasma powder cladding losses of cladding materials are inevitable. In order to increase the process effectiveness in this work the method of assessment of deposited bead mass at successive increase of weld pool dimensions on a wide and a narrow substrate was used to study the regularities of radial distribution of two-phase flows of microplasma-filler powder. It is established that experimental data of radial distribution of such flows on the anode surface are in satisfactory agreement with the normal distribution law. The method of calorimetry on a two-section water-cooled anode was used to evaluate the coefficient of concentration of specific heat flow of microplasma arc for cladding. It is shown that in the region of modes of microplasma cladding filler powder can be fed into the product plane with the concentration up to four times greater than the specific heat flow of the arc, and the ratio of effective diameters of powder feeding and heating spot is equal to 0.57-0.92. Influence of some design parameters of microplasmatron and process parameters of cladding on gas-powder flow concentration is described. Relationships between bead width, microplasmatron focusing nozzle diameter and characteristics of concentration of powder feeding into the weld pool required to limit filler powder losses within 1.44-2.56% at deposition of metal of less than 3 mm thickness on blade edges are established.