渗硼层高温硬度高,抗氧化性能好,但脆性大,提高渗硼层韧性是扩展实际工程应用的关键.文中在45CrNiMoV钢基体上采用电镀镍+高温扩散预处理,在表层形成γ-(Fe,Ni)层后,再用固体渗硼法制备出含镍渗硼层,并与直接渗硼层进行对比.用扫描电镜(SEM)、X射线衍射(XRD)和显微压痕法对镀镍渗硼层的截面形貌,组织结构及硬度分布和断裂韧性进行了研究.结果表明:电镀镍+扩散预处理能显著提高渗硼层的断裂韧性,淬火+低温回火热处理几乎不影响镀镍渗硼层断裂韧性,而对直接渗硼层则有显著降低.镀镍渗硼层中的γ-(Fe,Ni)相能有效缓解冲击载荷,提高渗层断裂韧性.
The boriding layers have widely potential applications in tribological and antioxidation in high temperature area due to their outstanding combined properties including high-temperature hardness and chemical inertness.However,the highbrittlness of boriding layer limits its application spreading,how to improve the brittleness is the key in practical use.In this paper the nickel-boriding layers were fabricated by the powder-pack method on γ-(Fe,Ni) layer prepared by electroplating nickel and diffusing heat-treatment on 45CrNiMoV steel.The micro-hardness and the fracture toughness of the boriding layer were investigated by micro-indentation test.The cross-section morphology and phase structure were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD).Results show that the fracture toughness of the nickel-boriding layer is improved considerably compared with that of the direct-boriding layer.The quenching and low-temperature tempering heattreatment has scarcely effect on the fracture toughness of the nickel-boriding layer,while it greatly decreases the fracture toughness of the direct-boriding layer.The γ-(Fe,Ni) phase embedding in nickel-boriding layer can buffer the external impact power and improve the fracture toughness availably.
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