38CrMoAl钢表面离子渗氮层剥落原因分析
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摘要
在生产中发现不同形状38CrMoAl钢产品进行离子渗氮时,易出现渗氮层剥落的现象。通过对剥落处的外观观察、渗层硬度梯度测试、渗层金相OM和SEM观察,对剥落原因进行了分析。结果表明:在实际生产中,38CrMoAl钢产品由于氧化脱碳层较厚、淬火畸变较大、加工余量较小等原因,极易出现氧化脱碳层加工去除不完全现象,残余的氧化脱碳层会导致渗氮层表面硬度下降,并且在渗层内易产生大量微裂纹,情况严重时,还会导致渗层表面出现剥落现象。
The ion-nitrided layer of 38 CrMoAl workpieces with different shapes often peels off in practice. After examination of the peeling sites,measuring the microhardness gradient of nitrided layer,and metallographic examination by OM and SEM,the reasons for peeling were analyzed. The results show that due to the thickness of the oxidation decarburization layer,the large distortion of quenching and the small machining allowance,the oxidation decarburization layer of 38 CrMoAl workpieces often cannot be removed thoroughly and the remaining part would decrease the hardness of nitrided layer. Meanwhile many microcracks appear in nitrided layer. All of these will lead to surface peeling of ion-nitrided layer in serious cases.
The ion-nitrided layer of 38 CrMoAl workpieces with different shapes often peels off in practice. After examination of the peeling sites,measuring the microhardness gradient of nitrided layer,and metallographic examination by OM and SEM,the reasons for peeling were analyzed. The results show that due to the thickness of the oxidation decarburization layer,the large distortion of quenching and the small machining allowance,the oxidation decarburization layer of 38 CrMoAl workpieces often cannot be removed thoroughly and the remaining part would decrease the hardness of nitrided layer. Meanwhile many microcracks appear in nitrided layer. All of these will lead to surface peeling of ion-nitrided layer in serious cases.
引文
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