“Welding and Testing” Academic Centre at the Bauman Moscow State Technical University, Moscow, Russia:

N. P. Aleshin, Director
M. V. Grigoriev, Deputy Director for Research
N. A. Shchipakov, Head of Laboratory, e-mail: shchipak@yandex.ru

All-Russian Institute of Aviation Materials, Moscow, Russia:
S. V. Nerush, Head of Laboratory

Additive technologies are widely used in various industries. The use of additive technologies provides new design possibilities, provides greater freedom in choosing the configuration of the product, its internal structure, which allows to optimize the mass and functional parameters of the part. One of the most characteristic types of additive manufacturing defects is porosity – volume-distributed micropores with a size of less than 40 microns. To ensure the quality of finished products created using additive technologies, it is necessary to develop non-destructive testing methods to determine the volume fraction of pores. In this article, the study of the volume fraction of pores of samples made by selective laser fusion technology was carried out. Various methods for determining the volume fraction of pores in products, their advantages and disadvantages are considered. Samples for research were made of two materials: corrosion-resistant steel and cobalt. The different value of the pore volume fraction in the samples was achieved by varying the modes and parameters of the selective laser melting process, in particular, the scanning speed and laser power. Some samples were subjected to hot isostatic pressing. The studies were carried out by comparing the results obtained in the study of sections and non-destructive ultrasonic method. The velocity of propagating longitudinal ultrasonic waves was determined experimentally in the study of samples by ultrasonic method. The correlation between the velocity of longitudinal waves and the volume fraction of pores in the samples is shown. It is seen that the qualitative dependences for corrosion-resistant steel and cobalt have the same character, and only the coefficients in the regression equations differ.

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