The possibility of obtaining spherical microgranules without satellites for surface-plastic deformation of responsible products

Abstract

Problem. To strengthen the surface-plastic deformation (SPD) of components of a responsible purpose, for example, in the aviation industry, working bodies (microspheres) are used, which can be obtained by the technology of gas atomization. Powders used for SPD of machine parts must be spherical without satellites with maximum monodisperses. Goal. The aim of this paper is to develop a process for obtaining spherical microgranules without satellites in the process of gas atomization and to study the quality parameters of the surface layer of parts treated with the use of microgranules as SPD working bodies. Methodology. To obtain spherical microgranules it is proposed to use the method of gas sputtering of a metal melt with the use of a progressive rotating gas stream. In the proposed method, the destruction of the jet and the subsequent destruction of individual small particles occur in the vacuum, which is created by two opposite directed helical gas flows. This leads to the expansion of the crushing zone of the metal, reducing the direct impact of the gas on the liquid metal particles and, thus, allows the separation of the motion of small and large droplets in space, which significantly reduces the probability of the formation of small satellites on the surface of larger particles. Spraying of a metal melt of ShH15 steel, heated to a temperature of 1580 оС, was carried out at a gas pressure of 1,4… 1,7 MPa, a melt flow of 0,5 kg/s and a specific gas flow rate of 1,0 m3 /kg. Results. The efficiency of the application of the obtained working bodies is proved by the results of the study of the operational properties of the surface layer of the parts being processed: surface roughness corresponds RA = 0,9...0,8 μm; the degree of deformed state reaches 18...30% at a depth of up to 120 microns; the residual compression stresses are 300...700 MPa at a depth of up to 100 μm. Scientific originality. The factors that influence the number of satellites on the surface of spherical microgranules are analyzed in the paper. It is established that the organization of the rotation of the gas flow around the axis of the atomization in the radial direction facilitates the process of removal of fine particles beyond the sputtering torch, which, in turn, leads to a decrease in the number of satellites on spherical powder particles. Practical value. According to the tests, the use of microspheres of ShH15 steel for SPD of a wide range of parts, gives significant technical and economic advantages in comparison with other methods: elimination of costs for surface finishing after SPD; increased by 10...30 % endurance of processed materials; increased by 2...6 times the durability of parts; 3 times increased product life.