Experimental Study of the Defect Layer on Workpieces, grown by the DMD method

Abstract

Introduction. At this time, new methods of manufacturing workpieces are gaining great popularity, for example, additive technologies. Methods for growing workpieces by sintering a powder with a laser make it possible to manufacture parts of complex shapes that are impossible or rather difficult to obtain by traditional methods, such as casting, forging, etc. However, the details, obtained by means of additive technologies, in particular the DMD method (Direct Metal Deposition), do not correspond with the accuracy requirements. Consequently, such workpieces require further processing by turning, milling or grinding. To design an operation for machining parts, it is necessary to know the machining allowances, the magnitude of errors formed during the blank operation, so that after its removal the processed part meets the requirements of the drawing. The purpose of the work: experimental study of the size of the defect layer in the near-surface layers of generative workpieces made of Stellite 6 and CuAl10Fe4, grown by DMD method, using microstructural methods. In the work, using a microscope, a study is carried out, which consisted in the visual determination of the defective layer, which differs in structure; measuring its size; carrying out a chemical analysis; determining the nature of the change in microhardness. The research method is a microscopic examination of deposited materials Stellite 6 and CuAl10Fe4 (CuAl10Fe4). From the pictures taken with a microscope, it is possible to establish the linear size of the defect layer. Results and Discussion. Vortex formations are found in the melting zone, its chemical analysis is carried out and it is found that the concentration of chemical elements in these areas changes and includes both elements of the powder material and the substrate material. Measurement of microhardness showed that it decreases with depth from the surface of the deposited material to the substrate. Thus, the use of the technique presented in this paper for microscopic studies of the structure, chemical composition and microhardness of workpieces, grown by the DMD method will allow to predict the value of processing allowances in the future, during the designing of mechanical processing operation of generative workpieces.