Interface microstructure and mechanical properties of selective laser melted multilayer functionally graded materials

Functionally graded material (FGM) can tailor properties of components such as wear resistance, corrosion resistance, and functionality to enhance the overall performance. The selective laser melting (SLM) additive manufacturing highlights the capability in manufacturing FGMs with a high geometrical complexity and manufacture flexibility. In this work, the 316L/CuSn10/18Ni300/CoCr four-type materials FGMs were fabricated using SLM. The microstructure and properties of the FGMs were investigated to reveal the effects of SLM processing parameters on the defects. A large number of microcracks were found at the 316L/CuSn10 interface, which initiated from the fusion boundary of 316L region and extended along the building direction. The elastic modulus and nano-hardness in the 18Ni300/CoCr fusion zone decreased significantly, less than those in the 18Ni300 region or the CoCr region. The iron and copper elements were well diffused in the 316L/CuSn10 fusion zone, while elements in the CuSn10/18Ni300 and the 18Ni300/CoCr fusion zones showed significantly gradient transitions. Compared with other regions, the width of the CuSn10/18Ni300 interface and the CuSn10 region expand significantly. The mechanisms of materials fusion and crack generation at the 316L/CuSn10 interface were discussed. In addition, FGM structures without macro-crack were built by only altering the deposition subsequence of 316L and CuSn10, which provides a guide for the additive manufacturing of FGM structures.