A carbide-free bainite steel of 0.29C–2.50Si-1.50Mn-1.0Mo-0.97Cr (wt.%) with no voids and cracks was fabricated via laser powder deposition (LPD). Different post-treatment plans were conducted and then microstructures and properties of the steel were studied through optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffractometry (XRD), transmission electron microscopy (TEM), hardness meter and tensile test machines. Obtained results show that the microstructure of the deposited specimen consisted of granular pearlite and retained austenite (RA). The yield strength, tensile strength and elongation were 662 ± 71 MPa, 1051 ± 65 MPa and 13.03 ± 1.33 %, respectively. After austempering at 578 K, the microstructure of the specimen changed to bainite ferrite (BF) and RA. Moreover, it was found that the yield strength and tensile strength significantly increased to 1156 ± 60 MPa and 1289 ± 110 MPa, respectively. However, it had poor strain hardening capacity and elongation remained unchanged. After hot rolling and austempering, the RA content of the specimen significantly increased and the strain hardening capacity improved. However, when the isothermal temperature was less than the Ms temperature (i.e. 553 K), the corresponding microstructure consisted of martensite, BF and 13.6 vol% of RA. In this case, the yield strength, tensile strength and elongation were 895 ± 74 MPa, 1157 ± 92 MPa and 14.59 ± 1.13 %, respectively, indicating slight improvement. Meanwhile, it was found that when the isothermal temperature exceeded Ms temperature, the mechanical properties improved significantly. The present study demonstrated that specimens with an isothermal temperature of 578 K had the best mechanical properties. In particular, the yield strength, tensile strength and elongation of the optimized alloy were 1177 ± 44 MPa, 1398 ± 57 MPa and 19.80 ± 0.79 %, respectively.

通过激光粉末沉积 (LPD) 制造无孔洞和裂纹的 0.29C–2.50Si-1.50Mn-1.0Mo-0.97Cr (wt.%) 无碳化物贝氏体钢。实施不同的后处理计划，然后通过光学显微镜 (OM)、扫描电子显微镜 (SEM)、X 射线衍射仪 (XRD)、透射电子显微镜 (TEM)、硬度计和拉伸仪研究钢的显微组织和性能。测试机器。获得的结果表明，沉积试样的显微组织由粒状珠光体和残余奥氏体（RA）组成。屈服强度、拉伸强度和伸长率分别为 662 ± 71 MPa、1051 ± 65 MPa 和 13.03 ± 1.33 %。在 578 K 等温回火后，试样的显微组织转变为贝氏体铁素体 (BF) 和 RA。而且，结果表明，屈服强度和抗拉强度分别显着增加到 1156±60 MPa 和 1289±110 MPa。然而，它的应变硬化能力很差，伸长率保持不变。经过热轧和等温回火后，试样的RA含量显着增加，应变硬化能力提高。然而，当等温温度低于M s 温度（即 553 K），相应的显微组织由马氏体、BF 和 13.6 vol% 的 RA 组成。在这种情况下，屈服强度、拉伸强度和伸长率分别为 895±74 MPa、1157±92 MPa 和 14.59±1.13 %，表明略有改善。同时发现，当等温温度超过M s 温度时，力学性能显着提高。本研究表明，等温温度为 578 K 的试样具有最佳的机械性能。特别是优化后的合金的屈服强度、拉伸强度和延伸率分别为 1177±44 MPa、1398±57 MPa 和 19.80±0.79%。