Formation and impact of functionally graded buffer layers between martensitic stainless steel and wrought steel substrate by laser metal deposition

In this study, the martensitic stainless-steel powder had been successfully deposited on the surfaces of 1045 wrought steel substrates using five types of laser metal deposition strategies. The results showed that a thin buffer layer can be naturally generated in-between the deposition layer and substrate owning to the dilution effect, producing functionally graded structures consisted of martensite dendrite matrices and intermetallic phases (e.g., M-23(C, B)(6)). Unfortunately, the poor deformation characteristic of natural buffer layers can exacerbate the risk of cracking, leading to an incompatibility between martensitic stainless steel and forming steel. A thick artificial buffer layer was then designed by addition of Inconel 625 powder. Because of the formation of graded austenite phase in the artificial buffer layer, the yield strength of specimen was enhanced significantly. Hence, our study can be used for manufacture of reliable moulds with high surface hardness and structural strength and may be helpful in further developing hybrid forming strategy in the field of mould manufacture. When subjected to stress impact during mould filling, the artificial buffer layer with functionally graded properties would have a perfect capability to bear the deformation as the load increased, dramatically improving the reliability and functionality of moulds. (C) 2021 The Author(s). Published by Elsevier Ltd.