Abstract
ABSTRACT In this paper, 20Mn2SiCrMo bainitic crossing noses were repaired by depositing 420SS, Stellite 6, 17-4PH and 18Ni300 alloys on the rail surfaces to form functionally graded materials (FGM) using laser directed energy deposition (L-DED) technology. As a result, only 18Ni300 deposit achieves an excellent strength-toughness combination, which possesses a yield strength of ∼1120 MPa together with an impact energy of ∼85.05 J, better than those of substrates (∼1071 MPa, ∼71.34 J). Besides, the wear and rolling contact fatigue (RCF) resistance of 20Mn2SiCrMo/18Ni300 FGM is enhanced to 2.7 and 23.6 times as much as those of substrates. Massive ultrafine nanoprecipitates and a small amount of austenite make 18Ni300 deposit strong enough as well as a certain work-hardenability, ensuring good wear resistance therein; the significant RCF resistance originates from the improved shakedown limit. Therefore, all findings reveal that 18Ni300 is the most promising depositing material for repairing bainitic crossing noses by L-DED.
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