High-speed laser directed energy deposition of Ni60 on 38CrMoAl steel: Crack inhibition and microstructure performance modulation via inductive preheating

To inhibit cracking and improve performance, Ni60 alloy layers were deposited on the 38CrMoAl steel substrate using an inductive preheating-assisted high-speed laser-directed energy deposition technique (IP-HS-LDED). The effects of the preheating temperature on the crack, element distribution, microstructure, and performance of the deposited layers were systematically investigated via experiment, finite element simulation, and theoretical analysis. The results revealed that substrate preheating reduced the residual stresses and amount of brittle and hard Cr7C3 particles in the deposited layers, thereby eliminating cracks. The deposited layers were primarily composed of gamma-Ni, Ni3B, Cr7C3, CrB, and ferrite. Compared with the deposited layer preheated to 500 degrees C, the size and content of Cr7C3-type carbides in the deposited layer preheated to 400 degrees C increased, thus the load transfer and dislocation strengthening effects were enhanced, and the hardness of the deposited layers increased by 72.6 HV. Because preheating to 400 degrees C produced aggregated and coarse Cr7C3 carbides, the significant mechanical property difference between the carbides and the substrate caused a large stress concentration between them during friction wear, easily leading to crack formation and the further development of spalling and weakening of friction performance. Abrasive wear was the main wear mechanism of the deposited layers.