Evaluation Reliability of Hybrid Surface Modification Material by Carburizing and Fine Particle Peening

(1)研究了真空渗碳和细颗粒强化复合表面改性对SCM415材料疲劳强度行为的影响。采用SCM415淬火、真空渗碳和混杂、真空渗碳和细颗粒喷淋试样，对其硬度分布、力学性能、疲劳强度和裂纹扩展进行了测试。在疲劳行为方面，研究了试件的裂纹扩展速率da/dN与应力强度因子范围ΔK、da/dN与有效应力强度因子范围ΔKeff、疲劳裂纹萌生寿命N_i和裂纹失效寿命N_f之间的关系。结果表明，复合表面改性能有效防止疲劳裂纹萌生和扩展。(2)对细颗粒强化过程中被击材料表面的颗粒速度和温度分布进行了数值分析。当采用直接加压方式加速时，计算出50μm颗粒在撞击金属表面之前的速度为222m/s。在施加空气压力时，细颗粒的加速度比大颗粒明显增加。实验值与计算值吻合较好。另一方面，温度分布表明，表面最高温度为1000K，并立即冷却。

(1)This study examines the effect of hybrid surface modification by vacuum carburizing and fine particle peening on fatigue strength behaviors of SCM415 material. We used quenched, vacuum carburized and hybrid, vacuum carburized and fine particle peened, specimen made of SCM415 and measured their hardness distribution, mechanical properties, fatigue strength and crack propagation. In terms of the fatigue behaviors, we investigated the relationship between the crack propagation rate da/dN and stress intensity factor range ΔK, da/dN and effective stress intensity factor range ΔKeff, as well as the fatigue crack initiation life N_i and crack failure life N_f of specimens. The results show specimens with hybrid surface modification are effective in the prevention of fatigue crack initiation and fatigue crack propagation.(2)This study examines numerical analysis of particle velocity and temperature distribution of struck material surface in fine particle peening. When the particle is accelerated using a direct-pressure type, the velocity of a 50μm particle, just before striking the metal surface, was calculated to be 222m/s. In applying air pressure, the acceleration of fine particles show significant increase compared to larger sizes. Moreover, the experimental values agree well with the calculated ones. On the other hand, the temperature distributions show the maximum surface temperature to be 1000K and cools instantly.