加涂PSR-1(NiCrBSi系)的FNA涂层气阀在生产上使用已超过6000小时,PSR-1合金是一由Ni—Cr固溶体和高硬度的硼,碳化物质点组成的多相结构,具有很好的耐磨耐蚀性。本文着重研究了该涂层合金在内燃机的燃气腐蚀疲劳工作条件下的演变规律,经对使用前后的涂层气阀分析解剖表明:涂层与基体之间的互溶区由富Ni固溶体转变成富Fe固溶体,影响到涂层组织和成分变化。分析指出:Fe在涂层中的扩散是硼化铬转变成含铁硼化铬的诱导因素,Cr的重新分布同样受Fe扩散所控制,硼在钢中扩散未导致气阀机械性能恶化,分析认为:在气阀使用工况下,PSR-1涂层组织稳定性是满意的。
An FNA-coated exhaust valve covered with PSR-1 coating(NiCrBSi)has lasted more than 6000hrs in service. The resistance of PSR-1 to wear and corrosion is due to its multiphase structure with Ni-Cr solid solution and boride and carbide particles of high hardness. In the present paper a study of the phase stability of this coating under corrosion fatigue condition in internal combustion engine is described. The analyses of the coated valves before and after service indicate that the composition of the intermediate layer-between coating and base material has changed from a solid solution rich in Ni to one rich in Feo It is found that, the diffusion of Fe results in transformation of chromium boride to iron chromium boride. The superior properties and longer life of the coated valves can be ascribed to the lower diffusion rate of Fe at the service temperature of about 600℃. The redistrubution of Cr in the coating alloy depends on the diffusion of Fe as well. The diffusion of boron has not induced deterioration of mechanical properties. In conclusion, the PSR-1 coating is Sa.tisfactory as to the phase stability after more than 6000hrs service
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