【摘要】 本文利用X光衍射仪、金相显微镜和声发射等手段对38CrMoAlA,35CrMo,40Cr钢经纯氨离子氮化,纯氨加钛离子氮化以及气体氨化后的渗层组织,硬度及干式滚动磨损性能进行了观察和分析。结果表明:加钛离子氮化可以显著提高工件渗层的硬度;但由于脆性增加而不利于干式滚动磨损;离子氮化处理后抗干式滚动磨损性能最佳。更多还原

【Abstract】 Nitriding hardening is nowadays one of the important processes in surface hardening for various steel grades. The behavior of rolling-wear resistance of some alloy structural steels with relation to nitrided case structure has been experimentally investigated and the result is reported in this article.Summary. Three kinds of steel as 38CrMoAlA, 35CrMo and 40Cr after different nitriding processes, ie. pure NH3 ionic, NH3 + Ti ionic and gaseous nitridings at the identical temperature of 520℃×8hr, have been observed and tested for their nitrided case structures, hardnesses and the unlubricated rolling-wear resistance by means of X-ray diffraction, metallographical test and sound emission etc. Comparing hardnesses and hardening penetrations measured, the highst microhardness and steepness of hardness profile with respect to depth belong to those steels treated by NH3 + Ti ionic nitriding. This is regarded mainly as due to the effect of dispersion hardening of alloying nitrides and the increase in dislocation density. The next two in order of hardness and steepness of hardness profile are pure NH3 nitriding and gaseous nitriding respectively.Unlubricated rol-ling-wear test was performed at a rotating speed of 400rpm under a load; of 150kg. Results as shown in figures 4,5 and 6 point out that in wear resist-ance the best is pure NH3 ionic nitriding and the gaseous nitriding is bad. Directly related to the brittleness of nitrided case, the compound layer in steel surface treated by NH3 + Ti ionic nitriding is considered unfavourable to rolling-wear resistance especially for 38CrMoAlA. The result is worthy to be considered in the choice of proper nitriding process for an alloy steel given.Fig.1 Hardness profile with respect to hardening depth of 38CrMoAlA NH3 + Ti ionic; °pure NH3 ionic;⊙gaseous nitriding.Fig,2 Hardness profile with respect to hardening depth of 35CrMo Fig.3 Hardness profile with respect to hardening depth of 40Crfig.4 Wear loss in weight of 38CrMoAlA with respect to wearing time pure NH3 ionic; NH3 + Ti ionic; gaseous nitriding;no nitrided.Fig.5 Wear loss in weight of 35CrMo with respect to wearing time Fig.6 Wear loss in weight of 40Cr with respect to wearing time Tab.1 Steel’s composition Tab.2 HT regime of specimen Tab.3 Depths of compound layer and nitrided case and surface hardnessafter different nitridingsTab.4 Relative quantities of e and γ’ phases after different nitridings Tab.5 Diffraction patterns of steels after different nitridings Tab.6 Load correspondent to first crack initiated, by sound emission. Photo 1 Microstructure of steel after different nitridings Photo 2 Frictional surface microstructure of steel after differentnitridings(a)after NH3 nitriding; (b)after NH3 + Ti nitriding;(c)no nitrided.更多还原