摘要
采用离子渗氮(PN)、离子渗碳(PC)及离子氮碳共渗(PNC)工艺对316L不锈钢进行表面硬化处理。利用光学显微镜(OM)、X射线衍射仪(XRD)、电子探针(EPMA)、显微硬度仪和振动样品磁强计(VSM)等分析手段对处理后的试验钢组织、显微硬度及磁性能进行表征。结果表明,采用PC、PNC、PN这3种工艺处理的试验钢均可获得膨胀奥氏体相,但是间隙原子含量逐渐增大,晶格膨胀程度逐渐加剧,分别为1.7%、4.1%和5.5%。PNC与PN处理的试样可获得更厚的渗层厚度和更高的表面硬度,表面硬度约为基体的4.5倍。此外,PN处理的试样具有铁磁性,PC和PNC处理的试样则呈现出与原始奥氏体不锈钢一致的弱磁性。与PNC工艺相比,PN处理的试样表现出更弱的Cr与N间相互作用及略大的晶格膨胀,铁磁性却显著增强。在316L不锈钢离子扩渗处理中,诱发顺磁到铁磁转变的首要因素为晶格膨胀,晶格膨胀增大了Fe-Fe原子间距,减少了3d轨道的重叠,从而增大了Fe原子磁矩,使铁磁性显著增强,磁相变的临界晶格膨胀处于4.1%~5.5%之间;次要因素为Cr与N之间的相互作用。316L不锈钢的无磁强化最佳工艺为PNC工艺,具体为温度420℃、阴极电压600 V、气压200 Pa、气氛N_(2)∶H_(2)∶CH_(4)=20∶77∶3、处理时间6 h。采用此工艺对316L不锈钢进行表面强化,可在其表面获得厚度大、硬度高、磁性弱的强化层。
Surface hardening of the 316L stainless steel was treated by using the process of plasma nitriding(PN),plasma carburizing(PC)and plasma nitrocarburizing(PNC),respectively.Microstructure,microhardness and magnetic properties of the tested steel were analyzed by means of optical microscope(OM),X-ray diffractometer(XRD),electron probe microscopic analyzer(EPMA),microhardness tester and vibrating sample magnetometer(VSM),respectively.The results show that the expanded austenite phase can be obtained on the surface of 316L stainless steel treated by all the three processes of PC,PNC and PN,and the content of interstitial atoms increases gradually,the lattice expansion increases,which is 1.7%,4.1%and 5.5%,respectively.The specimens treated by PNC and PN process can obtain thicker infiltrated layer and higher surface hardness,which is about 4.5 times of the substrate.In addition,the specimens treated by PN process show ferromagnetism,while the specimens treated by PC and PNC process show weak magnetism,which are consistent with the prior austenitic stainless steel.Compared with PNC process,the specimens treated by PN process exhibit weaker interaction between Cr and N and slightly larger lattice expansion,but the ferromagnetism are significantly enhanced.The lattice expansion that induces the magnetic phase transition of the 316L stainless steel treated by plasma diffusion process is the primary factor,which makes the expanded austenite transform from paramagnetism to ferromagnetism.The lattice expansion increases the Fe-Fe atomic distance and reduces the overlap of 3d orbitals,which resuits in the increase of magnetic moment of Fe atoms,and the ferromagnetism is significantly enhanced.The critical value of lattice expansion that causes the magnetic phase transition is between 4.1%and 5.5%.The interaction between Cr and N of that is the secondary factor.The optimum non-magnetic strengthening process for 316L stainless steel is PNC process,the process parameters are as follows:temperature of 420℃,cathode voltage of 600 V,pressure of 200 Pa,atmosphere ratio of N_(2):H_(2):CH_(4)=20:77:3,holding time of 6 h,at which the specimens can obtain a strengthened layer with large thickness,high hardness and weak magnetic properties.
作者
罗建东
杨颖仪
林育周
Luo Jiandong;Yang Yingyi;Lin Yuzhou(School of Mechanical and Automotive Engineering,South China University of Technology,Guangzhou Guangdong 510000,China;Shenzhen Huayufa Vacuum Ion Technology Co.,Ltd.,Shenzhen Guangdong 518000,China)
出处
《金属热处理》
CAS
CSCD
北大核心
2021年第7期207-211,共5页
Heat Treatment of Metals
基金
华南理工大学科研基金(x2jq-D170170)。
关键词
316L不锈钢
离子渗氮
离子渗碳
氮碳共渗
磁性能
显微组织
316L stainless steel
plasma nitriding
plasma carburizing
plasma nitrocarburizing
magnetic properties
microstructure
