Abstract
In order to effectively eliminate the crack initiation, reduce the amount of pores and improve the structure of large alloy steel parts with high-performance, the direct laser deposited (DLD) technique was used to prepare the 24CrNiMoY alloy steel samples by laser depositing power of 2000W and scanning speed of 6 mm/s at 100 °C,150 °C, 200 °C, 250 °C preheating temperatures, respectively. The structure and properties of the samples were studied using OM, SEM, XRD, TEM, EBSD, hardness tester and tensile tester. The results showed that with the increase of preheating temperature, the cracks in deposited alloy steel samples were removed, and the amount of pore was significantly reduced. The structure of the samples were mainly composed of granular bainite (GB) and lath bainite (LB), the content of LB was reduced from 95.7% to 3.5% with the increase of preheating temperature because GB played a segmentation role to LB. When the preheating temperature was 200 °C, the deposited sample with GB (34.7%) and LB (65.3%) had the most uniform microhardness distribution, the highest microhardness of 414 HV0.2, and the best match of strength and toughness with the tensile strength of 1051 MPa and the elongation of 7.4%. The proper preheating temperature of 200 °C can effectively eliminate the crack, decrease the pores and significantly improve the structure and properties of the DLD 24CrNiMoY alloy steel.
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