Crater Formation On The Surface Of Metals And Alloys During High Power Ion Beam Processing

Nuclear Instruments and Methods in Physics Research B 148 (1999) 154±158 Crater formation on the surface of metals and alloys during high power ion beam processing V.A. Shulov b a,* , N.A. Nochovnaya b a Moscow Aviation Institute, 4 Volokolamskoye shosse, 125871 Moscow, Russian Federation All-Russian Institute of Aviation Materials, 17 Radio Street, 107005 Moscow, Russian Federation Abstract The e€ect of high-power, pulsed ion-beam irradiation and various methods of the preliminary surface treatment on the crater formation process was examined using Auger electron spectroscopy, X-ray di€raction analysis, and scanning electron microscopy. The crater distribution density, sizes and shape, along with their microhardness and chemical composition inside and outside them were determined. As a result of these experiments, the most probable mechanisms of crater formation on the surface of refractory alloys were established. Ó 1999 Elsevier Science B.V. All rights reserved. PACS: 34.50.D Keywords: Ion beam; Crater formation; Service properties; Surface 1. Introduction It is well known that crater formation on the solid surfaces, when irradiating them by highpower pulsed, ion-beams (HPPIB) [1] leads to the catastrophic deterioration of the property level (fatigue strength, oxidation resistance, salt corrosion resistance etc.) [2±4] of irradiated components. As a result, the determination of crater formation mechanisms and the development of methods allowing to decrease the negative in¯uence of already formed craters upon the operating * Corresponding author. Tel.: +7 095 158 4424; fax: +7 095 158 2977; e-mail: [email protected]®pc.ru characteristics of irradiated components are the most important factors. The objective of the present research is the investigation of such e€ects as the preliminary surface treatment and irradiation conditions (particularly pulsed ion current density) on the crater formation process. 2. Experimental The studied samples were made of bars, produced of the following refractory alloys: VT8M (Ti±6Al±3.7Mo±0.2Fe±0.3Si), VT9 (Ti±7Al± 3.8Mo±0.2Fe±2.5Zr±0.3Si), VT18U (Ti±6A1± 3.4Mo±0.2Fe±4.5Zr±1.5Nb±0.25Si±3Sn), VT25U (Ti±7A1±2.5Mo±1.5W±0.2Fe±2.5Zr±0.25Si), 0168-583X/98/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 8 ) 0 0 8 4 5 - 3 V.A. Shulov, N.A. Nochovnaya / Nucl. Instr. and Meth. in Phys. Res. B 148 (1999) 154±158 EP866sh (Fe±2.5Ni±16.5Cr±1.6Mo±1W±0.3Nb± 5.5Co±0.6Si), and EP718ID (Ni±33Fe±2.4Ti± 16Cr±1.4A1±5.2Mo±3.5W±1.5Nb±0.6Mn±0.3Si) with the use of machining. The irradiation of these targets (14 ´ 7 ´ 3 mm3 ) were carried out using the TEMP accelerator [4] by carbon (70%) and proton ion beams under the following conditions: ion energy ± 300 keV (E), pulse duration ± 50 ns (s), and the ion current density in a pulse (j) as well as the number of pulses (n) were varied from j ˆ 20 A cmÿ2 , n ˆ 1 up to j ˆ 220 A cmÿ2 , n ˆ 100. After the irradiation some targets were studied by Auger electron spectroscopy (AES), X-ray di€rac