Experimental investigation of surface roughness of liquid rocket engines parts manufactured with additive technologies

Modern development of additive manufacturing forms tasks of re-engineering of the existing design solutions and implementation of 3D printing technologies for new parts manufacturing. Nowadays, there is a large number of the process categories of “metal” additive manufacturing every of which is based on different principles and bears individual features. One of the most widely used process is a “single step” Powder Bed Fusion during which building parts are produced for a single operation. A focused laser beam is utilized as a heat source so that words collocation Laser Powder Bed Fusion (L-PBF) is used to address the process. L-PBF process is applied in the most different fields: aviation, space, biotechnical and other industries. One of the most appealing aerospace applications for production of complex parts of the liquid propellant rocket engines. A wide nomenclature of the available powder materials and relatively low requirements for technical level of equipment of the production site may be used for reasoning of the phenomena of growing popularity. One of the features of the L-PBF process is relatively high roughness of the produced surfaces which should be considered while designing of hydraulic tracts. There is a “stair-step effect” which contributes to roughness increase due to layer-based process which depends heavily on surface orientation during the building of the part, its location on the building plate, etc. Surface roughness of the L-PBF-manufactured parts is the subject of the experimental investigation of this work. The effect of the roughness change according to the part orientation and building direction is experimentally investigated on the test plates and inner surfaces of the swirl injectors specimens. All investigated specimens were built from Inconel 718. Four variants of the design types of swirl injectors specimens were investigated. The dependency of the roughness parameters versus inclination angle of the surface was obtained after the carried out analysis of the experimental data. Harmonic trigonometric dependencies are proposed for the roughness prediction. The proposed model accuracy is verified using Fischer criteria with =0.05.