Improvement of resistance to corrosion of stainless steel 304 in acid solutions by simultaneous deposition with doping o
- PDF / 583,504 Bytes
- 6 Pages / 593.28 x 841.68 pts Page_size
- 39 Downloads / 227 Views
Hideyuki Murakami and Hiroshi Takai Tokyo Denki University, Faculty of Engineering, 2-2, Kanda-Nishi-Cho, Chiyoda-ku, Tokyo, 101 Japan (Received 11 July 1990; accepted 27 July 1990) The chemical stability of the surface of stainless steel (SUS) 304 in acid immersion tests is greatly improved by the laser implant-deposition (LID) process, i.e., the simultaneous deposition and incorporation of silicon by KrF excimer laser irradiation. The etching depths of the treated samples in 1.32 N HC1 solution are substantially zero at the laser irradiation conditions of more than 40 pulses and of more than 400 mJ/cm2 at the surface. By the quantitative verification of cathodic polarization in 1 N H2SO4, the highest polarization resistance is estimated to be 26.7 times that of the nontreated sample.
I. INTRODUCTION
Some of the mechanical, chemical, and physical properties of metals are greatly improved by the addition of suitable amounts of different species of atoms to the bulk, while other properties are apt to be deteriorated. However, if the different species of atoms are confined only to the surface layer by doping and/or coating, metal surfaces having improved chemical and physical properties relative to corrosion, friction, and wear can be created without impairing the original properties of strength and toughness of the bulk. Such surface modifications have been widely investigated. Materials with modified surfaces have been obtained by means of laser beam irradiation,1"5 ion implantation,6"10 plasma,11"13 and thermal processing.14"16 In order to modify the surface more efficiently, it is important to choose suitable atom species doped and/or coated to the metals. It is well known that many surface properties of metals are improved by doping and coating of Si to the bulk.516"18 A thin Si layer formed on stainless steel (SUS) 304 and 430 by molecular beam epitaxy (MBE) under the co-implantation of Si ions is a very useful technique for increasing corrosion resistance.18 However, the process must be carried out in an ultra-high vacuum chamber. More recently, Si diffusion coating on various steels of iron, low carbon steel, 9% Cr/1% Mo steel, and SUS310 has been performed by thermal treatment above 500 °C using 0.5% SiH4 gas in hydrogen.16 The technique has reduced oxidation, nitriding, or coking at high temperature or corrosion in mineral acids. However, the whole of the materials has been exposed to high temperatures, above 500 CC, during the process. J. Mater. Res., Vol. 5, No. 12, Dec 1990
http://journals.cambridge.org
Downloaded: 13 Mar 2015
On the other hand, we have demonstrated surface hardening of SUS304 resulting from the process of doping and simultaneous deposition of Si by irradiation of a KrF excimer laser beam in a SiH4 gas ambient.5 The surface hardness has been shown to be an increasing function of both the number of laser pulses and laser fluence. The deposited films have shown good adhesion to the substrates, since the Si atoms distribute continuously from the metal substrate to the films. The specif
Data Loading...
