Effect of Microstructure and Residual Stress on the Wear Resistance and Thermal Fatigue of 24CrNiMo Alloy Steel Formed Using Laser Direct Metal Deposition

In this work, 24CrNiMo alloy steel specimens were successfully prepared using laser direct metal deposition (LMD). The relationships between their microstructure, residual stress, as well as their thermal fatigue and wear properties for different types of treatments were then investigated. The treatments included quenching and tempering (QT), and stress relief annealing (SR) of the prepared samples. The study provided clear evidence that grain refinement was achieved after the QT and SR treatments. The hardness for the as-deposited specimens was found to be 325-380 HV 0.2 , while for the samples obtained after the QT and SR treatments, their values were obtained to be about 390 HV 0.2 and 355 HV 0.2 , respectively. In comparison to the as-deposited samples, the QT treated specimens were reduced from a larger tensile stress of 176 ± 96 MPa to − 14 ± 5 MPa, while the SR specimens were reduced from 176 ± 96 MPa to − 44 ± 10 MPa. The microstructure and residual stress transformation resulted in improved wear resistance and thermal fatigue properties of the specimens, where the wear weights of the as-deposited specimens were about 13 and 3.7 times higher than that for the QT and SR processed specimens. Overall, a significant improvement in the mechanical properties of the QT treated specimens was achieved.