MICROSTRUCTURE AND PROPERTIES OF PARTS PRODUCED BY DIRECT LASER DEPOSITION OF 316L STEEL POWDER

Direct laser deposition of metal powders is one of the additive methods of functional product manufacturing. It consists in metallic powder melting with laser beams in the inert gas atmosphere. Main process parameters include laser beam power, speed, scanning strategy and powder consumption. Each of the parameters is selected depending on the alloy type that jointly affects the structure and defect formation in products. The present paper shows that the experimental rectangular specimens of powder austenitic steel 316L were obtained by direct laser deposition. The microstructure and fractures of samples were studied using scanning electron microscopy in order to determine the structural features and identify any defects (pores, holes, crystallization cracks and oxide inclusions). Uniaxial tensile tests and hardness tests were carried out. The effect of laser beam scanning strategy on the microstructure and properties of samples when melting was analyzed It was observed that a dispersed structure with an average crystallite size of 1,3–1,9 μm is formed at 250 W laser power and 16 mm/s scanning speed that causes a high level of mechanical properties of experimental samples. It was shown that tensile strength at the lengthwise strategy (along the largest sample size) was up to 730 MPa with an elongation rate 25 % that exceeded 316L steel mechanical properties by 110 MPa.

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