Stainless Steel Thin Films Research Articles

Structural and magnetic study of bcc 304 stainless steel thin films elaborated by ion sputtering

A new method is presented for elaborating 304 SS thin films exhibiting both a bcc single phase and a strongly ferromagnetic structure. In the case of A1 substrate, the average hyperfine field as estimated by Mössbauer effect is 26.6 T and the angle between the spins and the film normal is 54° which is close to the random value. Using the field to estimate the magnetic moment, a value of 1.8μ B was deduced. Finally ion implantation is shown to slightly increase the average field; this phenomenon has been connected to a negative pressure effect.

Preparation of alloy thin films by the CAPD process

Brass (CuZn), nickel-silver (CuZnNi) and stainless steel (Fe18Cr8Ni) thin films were deposited by the cathodic arc plasma deposition process onto SUS304 in order to study the chemical composition change from that of the target and to determine surface roughness. The deposition variables investigated were substrate temperature and arc current. The chemical composition of each target and the prepared thin films were analyzed by atomic absorption spectrochemical analysis. The composition of both the brass and nickel-silver alloy films were studied in relation to the targets used as a function of substrate temperatures. Surface roughness was measured by the stylus method. As-deposited thin films displayed very high roughness.

Microporosity in 304 stainless steel films prepared by vapor quenching

Abstract Thin films of type 304 stainless steel composition were d.c. planar magnetron sputter deposited onto chilled and elevated temperature metallic and non-metallic substrates within the thickness range from 40 nm to 3.5 ωm. Bright field and dark field transmission electron microscopy and electron diffraction techniques were utilized to investigate the as-deposited thin films. A b.c.c. microcrystalline grain structure was obtained through vapor quenching at substrate temperatures (deposition temperatures) between 77 and 473 K. The use of a defocus contrast technique and stereomicroscopy revealed a high density of intergranular and intragranular microvoids in all the films investigated. Microvoids were not observed in 304 stainless steel films sputter deposited by other investigators under similar conditions. Interconnected void networks did not exist in thicker regions of the film but were present in a “channel” in thinner film regions. Both the microcrystalline grain size and the void structures were influenced by the deposition temperature. In this study an attempt is made to evaluate the 304 stainless steel thin film microstructures in the light of their potential for protective coating uses.

Dynamic in situ high voltage electron microscopy studies of tensile cracks in thin stainless steel films

The results of in situ straining of many thin micro-tensile specimens in a high voltage electron microscope provide both an overview and microstructural details of propagating cracks in 304 stainless steel. Sequences of highly magnified views of the crack tip show it to be a highly plastic region. Voids form in advance of the crack tip in most instances and these voids form crack precursors which link up with the crack tip to advance it. Sequences of electron micrographs of crack advance at magnifications ranging from 60x to 30 000x illustrate the process as one of crack growth, void (hole) growth and coalescence, crack growth etc. Plastic deformation associated with crack advance and fracture is highly localized within individual grains or grain portions (the grain size of the material was 15 μm). The crack-tip region and the edges of cracks are observed to have been partly or mostly transformed to α'-martensite (b.c.c.). Consequently, a propagating crack in 304 stainless steel creates a localized magnetic region as it propagates.