氮碳共渗钢的拉伸特性

本文对45钢氮—碳共渗不同冷却方式的拉伸特性进行了研究。试验得到一种新的锯齿状拉伸曲线和与之相对应的三区域断口特征。拉伸曲线和断口特征与冷却方式有关,并对此进行了分析。     

密封圈的失效分析

经碳氮共渗淬、回火热处理的密封圈,其表面获得高的硬度和良好的耐磨性,心部具有良好的综合性能,但在使用过程中易发生变形而破裂.采用金相检验和显微硬度测定等方法对失效件进行了分析,并与合格件进行比较.结果表明,导致密封圈变形而破裂的原因是选用的ST12钢含碳量太低,应选用含碳量和强度稍高的材料来制造.     

氮气-甲烷离子氮碳共渗工艺的研究

利用金相显微镜、扫描电镜和X射线衍射仪对经氮气-甲烷离子氮碳共渗的40Cr钢进行了分析,并测定了渗层中沿层深方向的显微硬度分布.结果表明渗层可分为3层,即化合物层、扩散层和基体组织.表面渗层物相结构主要由氮(碳)ε化合物和Fe3C构成;在适当的工艺条件下,可以获得表层硬度高达525 HV(0.1),沿层深方向硬度分布合理、脆性低的渗层;与常规离子渗氮相比,以氮气-甲烷混合气体作为气源的离子氮碳共渗工艺成本低廉,绿色环保.     

球墨铸铁件软氮化后加工形成的石墨坑对表面质量的影响

介绍了粗糙度的定义,指出球墨铸铁件在软氮化后进行珩磨加工时形成的石墨坑对表面质量的影响,并提出相应的表面质量控制方法。     

结构钢氮碳共渗后韧性下降的原因分析

探讨了结构钢经氮碳共渗处理后其冲击韧性值下降的原因。通过金相分析、扫描电子显微镜对渗层的观察及对一些工艺参数的分析，得出其主要原因是共渗过程中由于氢渗入基体，同时在晶界形成Fe-N化合物，结果导致结构钢变脆。采用去氢退火方法可除去大部分氢，同时会使Fe-N化合物穿晶析出，降低了Fe-N化合物在晶界附近偏聚程度，减少了沿晶脆断倾向，显著提高结构钢经N-C共渗后的冲击韧性值。     

Effect of Rare Earth Elements on the Impact Wear Resistance of Nitrocarburizing Layers

In this paper the effect of rare earth elements on the toughness and impact wear resistance of nitrocarburiz-ing layers is studied.The experimental results show that the toughness and impact wear resistance ofRE-nitrocarburizing layers are increased significantly compared with that of conventional nitrocarburizing lay-ers.The service life of hot die for manufacturing bicycle bolts increased more than 100%.The impact wearmechanism of RE-nitrocarburizing layers is investigated by SEM as well.     

Effect of treating atmosphere in plasma post-oxidation of nitrocarburized AISI 5115 steel

In this study quenched and tempered AISI 5115 steel was plasma-nitrided and nitrocarburized at 550 °C for 5 h in atmospheres of 80% N₂ balanced with various amounts of CO₂ and H₂ gases. The amount of CO₂ varied from 0 to 10 vol%. The highest amount of ε phases was formed in the compound layer after treating in atmosphere containing 7 vol% CO₂. Optimized compound layer was post-oxidized for 1 h at 450 °C under O₂/H₂ volume ratios of 1/1 and 3/1 as well as 100% oxygen. The treated samples were characterized using metallographic techniques, XRD, SEM, roughness measurement and potentiodynamic methods. The results showed that the growth rate of the oxide layer increased with increasing O₂ in the oxidizing gas mixture. X-ray diffraction analysis of oxidized layers confirmed the formation of highest amount of magnetite at post-oxidation in an atmosphere with the O₂/H₂ volume ratio of 1/1. Electrochemical polarization tests proved the enhancement of corrosion resistance by plasma post-oxidation and the highest corrosion resistance obtained after oxidizing under an O₂/H₂ volume ratio of 1/1.     

The Influence of Method of Carburizing and Nitrocarburizing on the Microstructure and Properties of Tool Steels

The paper presents the results of wear and metallography tests of tool steel grades: ASTM A681, ChI2M and Ch12FS per GOST, AMS 6437E i BS X46Cr13, all surface hardened by the Carbo process (carburizing) and by the NiCar process (nitrocarburizing). The therrno-chemical treatment was conducted in powder pack for a duration of 6 h (carburizing) and for 4 h in the case of nitrocarburizing. Factors investigated were: morphology, depth and microhardness of the cases obtained, their microstructure, as well as phase composition. Wear tests were conducted by the three cylinder-cone method.Wear velocity was 0.58 m/s, unit load was 50 MPa and 400Mpa, wear path was 3470 m. Oil SAE30 was applied at the rate of 30 drops per minute.     

Plasma and Gaseous Nitrocarburizing of C60W Steel for Tribological Applications

A comparison has been made between plasma and gas nitrocarburizing processes for C60W steel in terms of structural features of the layers and the tribological properties of the specimens. Gaseous treatments were performed in a sealed quench industrial furnace in optimized process cycles. For plasma nitrocarburizing, a semi - industrial size unit was operated at a range of process parameters. Experimental results indicate that increasing the treatment time increases the thickness of the compound layer but lowers the wear resistance. Plasma treatment produced a more effective case depth compared with gaseous process, providing a better uniformity. Analysis of X-ray diffraction patterns indicated that the compound layer in gas nitrocarburizing consisted of both e and γ‘ phases, whereas in plasma nitrocarburizing the ε phase was not detected.     

化合物CeCl_2对4Cr5MoV1Si钢气体软氮化过程的影响及生产应用

在通氨滴醇气体软氮化的基础上加入不同量的稀土化合物CeCl_2,研究了它对动力学过程、渗层组织结构,硬度及耐磨性的影响.结果表明:与常规软氮化过程相比,CeCl_2可使渗速提高20～30％,渗层的N、C含量增高,且向内层延伸分布,使表面硬度和耐磨性大大挺高;稀土元素Ce亦被渗入钢的表面,不仅起到催化活化渗入介质的作用,同时还可能起到微合金化的作用。