1、附录一英文翻译原文 EFFECT of ION NITRIDING ON the MICROSTRUCTURE AND PROPERTIES of MARAGING STEEL (250 GRADE) Kishora ShettyS. Kumarb,P. Raghothama Rao；Regional Centre for Military Airworthiness (Foundry and Forge), CEMILAC, DRDO, Bangalore-560 037, India Department of Materials Engineering, Indian Institute
2、 of Science, Bangalore-560 012, India Received 25 June 2008. Accepted 28 November 2008. Available online 10 December 2008 Abstract In the present investigation, ion nitriding of Maraging steel (250 grade) has been carried out at three different temperatures i.e., at 435, 450 and 465 for 10 h duratio
3、n in order to achieve good wear resistance along with high strength required for the slat track component of aircraft. The microstructure of the base material and the nitrided layer was examined by optical and scanning electron microscope, and various phases present were determined by X-ray diffract
4、ion. Various properties, such as, hardness, case depth, tensile, impact, fatigue properties and corrosion resistance were investigated for both un-nitrided and ion-nitrided materials. It is observed that the microstructure of the core material remains unaltered and Fe4N is formed in the hardened sur
5、face layer after ion nitriding at all the three temperatures employed. Surface hardness increases substantially after ion nitriding. Surface hardness remains almost the same but case depth increases with the increase in ion nitriding temperature due to greater diffusivity at higher temperatures. Ten
6、sile strength, fatigue strength and corrosion resistance are improved but ductility and energy absorbed in impact test decrease on ion nitriding. These results are explained on the basis of microstructural observations. The properties obtained after ion nitriding at 450 C for 10 h are found to be op
7、timum when compared to the other two ion nitriding temperatures. Keywords： Ionnitriding；Maragingsteel；Microstructure；Casedepth； Tensileproperties；Fatigue properties 1. Introduction Surface engineering means engineering the surface of a material or component to confer surface properties, which are di
8、fferent from the bulk properties of the base material1. The purpose may be to reduce wear, minimize corrosion, increase fatigue resistance, reduce frictional energy losses, act as a diffusion barrier, provide thermal insulation, exclude certain wave lengths of radiation, promote radiation, electroni
9、c interactions, electrically insulate or simply improve the aesthetic appearance of the surface. Surface engineering processes may broadly be grouped in three categories as (a) modifying surfaces without altering the substrates chemical composition； these types of processes include transformation ha
10、rdening, cold deformation, machining and peening, (b) changing the chemistry of the surface region； these types of processes include carburizing, nitriding, anodizing and ion implanting, and (c) adding a layer of material to the surface； these types of processes include weld overlay, painting, metal
11、 spraying, plasma spraying, electroplating, bonding, physical vapor deposition and chemical vapor deposition. Nitriding is a surface-hardening process by the introduction of nitrogen into the surface of steel2. Process methods for nitriding include gas nitriding, liquid or salt bath nitriding and pl
12、asma or ion nitriding. In gas nitriding this is done using a mixture of ammonia gas and dissociated ammonia in suitable proportions. In plasma or ion nitriding a glow discharge technology is used to introduce nascent (elemental) nitrogen to the surface of a metal part for subsequent diffusion into t
13、he material3,4and5. The plasma assisted surface modification techniques offer a great flexibility and are capable of tailoring desirable chemical and structural surface properties independent of the bulk properties3. It has other advantages, such as, no or very thin white layer forms after nitriding and there is no machining or grinding involved after the process, which is
