Investigation of mechanical properties for hybrid deposition and micro-rolling of bainite steel

Wire and arc additive manufacturing (WAAM) with a high efficiency and a low cost, is a novel technology for mass popularity. However, a relatively low deposition accuracy and lack of microstructure performances limit the further development of this method. In this paper, the hybrid deposition and micro-rolling (HDMR) process has been used to eliminate the ubiquitous anisotropy in the WAAM bainitic steel samples. To overcome the problems of deficient deformation and large remelted area resulting from the deep penetration and high temperature gradient, an initially optimized micro-rolling morphology based on decreasing the depth of penetration and increasing the ratio of width to reinforcement has been used. Besides, the rolling method with a rapid cooling rate near the temperature for austenite non-recrystallization region, has been used to increase the crystallinity. The results are shown below: the tensile strengths for the optimized sample are 1275 MPa, 1256 MPa, and 1309 MPa, corresponding to the transverse (X), longitudinal (Y), and perpendicular (Z) directions, respectively. The elongations for these three directions are 17.4%, 16.6%, and 17.7%. The average impact toughness is 99 J/cm2, and the average grain size is about 7 μm. As compared with the traditionally heavy rolling equipment, the new micro roller technology has been indicated as a lower cost method, for achieving outstanding mechanical properties.