Effect of 3D printing mode on structure and fatigue strength of 30CrMnSi steel

The desire of modern manufacturers to reduce the cost of producing goods leads to an increased search for ways to obtain the raw materials for future products more efficiently. One promising method for obtaining raw materials is electric arc surfacing (WAAM), which is discussed in this paper. The aim of the study was to investigate the effect of electric arc surfacing on the structure and fatigue strength of 30CrMnSi steel. To obtain the samples, two walls were surfaced according to the specified modes: I = 150 A, U = 25 V, Q = 600 J/mm (mode 1 ) and I = 110 А, U = 17 V, Q = 300 J/mm (mode 2 ). During the study of the walls microstructure after milling, it was found that when the metal is surfaced according to the mode 1 , large accumulations of technological defects such as pores and bad welding form in the material. When the metal is treated according to the mode 2 , these macroscopic defects are practically not detected. During optical emission analysis, it was observed that during the surfacing process, alloying elements are consumed and the carbon content decreases most actively. It should be noted that the burnout of elements occurs more actively when the metal is surfaced using the mode 1 . This may be due to the higher energy input in this process. A predominant ferrite-sorbite structure was found in the metal surfaced using the mode 1 . However, local ferritic colonies were revealed on the surface of the samples due to their height. The microstructure of the samples produced using the mode 2 is mainly composed of ferrite and pearlite. Ferrite is isolated as closed grids along the boun­daries of the austenitic grains, and traces of a Widmanstetten structure can also be seen. Perlite is present both as highly dispersed plates and partially spheroidized colonies. Despite the fact that the structure of the samples produced using the mode 1 is generally considered to be more favo­rable in terms of material properties, the fatigue strength of the samples produced according to the mode 2 exceeds that of the mode 1 by an average of 70 %. This may be due to the stronger influence of technological defects on the metal fatigue resistance than microstructural ones.