<正> 一、引言 金属表面的激光相变硬化处理具有变形小、淬火速度快,能局部选择性硬化等独特优点。对于那些在腐蚀介质和应力共同作用下,同时又需要耐磨的工件,则需要了解激光处理区表面的残余应力状态及其腐蚀行为。近几年来有许多关于激光相变硬化处理的应力状态和腐蚀行为研究的报导。本工作就东风40机车的50CrV钢传动簧片经激光硬化处理后其硬化区和热影响区的应力状态和腐蚀性能进行了研究。
Plate of spring steel 50CrV for making driving leafspring of locomotive was surface hardened by CO_2 laser beam. The hardened zonee was characterized by a microstructure with very fine martensite and trace of residual austenite. Measurements of the surface residual stress were performed. The results showed that the surface stress state was compressive in the hardened zone, while it was tensile in the heat effected zone, and that the change of hardness was in good agreement with the change of the stress from compressive to tensile. Obviously, the compressive state of the stress in the hardened zone may be due to the volume expansion associated with the martensitic transformation. Corrosion potential distribution and dynamic potential polarizatign behaviour of the laser hadened zone in dilute solutions of Na_2SO_4, NaOH and H_2SO_4 etc. was studied. It followed that the hardened zone exhibited higher corrosion resistance than both it's vicinity of heat effected zone and the untreated substrate. The passivation range of the laser hardened zone widened significantly and the corrosion current of passivation range decreased greatly, in some, cases, by nearly one order of magnitude as compared with that of untreated substrate. The corrosion behavior was discussed in relation to it's characteristic microstructure and stress state of the laser hardened zone.
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