Nb添加对LPBF成形18Ni300模具钢拉伸和磨损性能的影响

Effect of Nb Addition on Tensile and Wear Properties of 18Ni300 Mold Steel Fabricated by LPBF

摘要:

激光粉末床熔融（LPBF）技术凭借其制造复杂形状的卓越能力和调控微观结构的出色性能，在制备18Ni300模具钢方面极具优势，并且在注塑、压铸以及冲压模具等领域有着广泛应用。在模具钢中添加增强颗粒是提升其性能的有效手段。采用2种不同粒径的Nb粉末，利用LPBF技术制备了Nb/18Ni300复合材料，并对其微观结构和力学性能展开研究。结果显示，未熔Nb颗粒在基体中均匀分布且细化了基体晶粒，尤其是细粒径的Nb颗粒。此外，颗粒与基体间发生了元素扩散。18Ni300基体的主相为α-Fe和少量γ-Fe。添加Nb后，部分α-Fe转变为γ-Fe，并出现未熔Nb相。Nb的加入还提高了复合材料的硬度和耐磨性能，但略微降低了其拉伸性能。时效处理后，熔池和晶界变得模糊，晶粒进一步细化，颗粒周围的界面变薄。时效处理还促进了逆转奥氏体的形成。基础合金的硬度、极限抗拉伸强度以及体积磨损率分别达到51.9 HRC、1704 MPa和17.8×10^?6 mm³/(N·m)；相比之下，添加了细Nb颗粒的样品具有最大的硬度（56.1 HRC）、极限抗拉伸强度（1892 MPa）和屈服强度（1842 MPa），添加粗Nb颗粒样品的体积磨损率降低了90%，降至1.7×10^?6 mm³/(N·m)。

Abstract:

Laser powder bed fusion (LPBF) is highly suitable for forming 18Ni300 mold steel, thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures. It is widely used in fields such as injection molding, die casting, and stamping dies. Adding reinforcing particles into steel is an effective means to improve its performance. Nb/18Ni300 composites were fabricated by LPBF using two kinds of Nb powders with different particle sizes, and their microstructures and properties were studied. The results show that the unmelted Nb particles are uniformly distributed in the 18Ni300 matrix and the grains are refined, which is particularly pronounced with fine Nb particles. In addition, element diffusion occurs between the particles and the matrix. The main phases of the base alloy are α-Fe and a small amount of γ-Fe. With the addition of Nb, part of the α-Fe is transformed into γ-Fe, and unmelted Nb phases appear. The addition of Nb also enhances the hardness and wear resistance of the composites but slightly reduces their tensile properties. After aging treatment, the molten pools and grain boundaries become blurred, grains are further refined, and the interfaces around the particles are thinned. The aging treatment also promotes the formation of reverted austenite. The hardness, ultimate tensile strength, and volumetric wear rate of the base alloy reach 51.9 HRC, 1704 MPa, and 17.8×10^-6 mm³/(N·m), respectively. In contrast, the sample added with fine Nb particles has the highest hardness (56.1 HRC), ultimate tensile strength (1892 MPa) and yield strength (1842 MPa), and the volume wear rate of the sample added with coarse Nb particles is reduced by 90% to 1.7×10^-6 mm³/(N·m).