Tadashi Komori

Surface modification of stainless steels by in-line dry coating technology☆

Abstract In order to develop additional surface functions such as excellent corrosion resistance and decorative colours on stainless steels, plasma-assisted coating processes utilizing sputtering, ion plating and plasma chemical vapour deposition (CVD) have been assessed. In this study, the process parameters controlling corrosion-resistant and chromatic properties were investigated. Guidelines for selecting suitable processes and coating conditions were established. Plasma CVD is one of the most suitable processes for the production of excellent corrosion-resistant coatings such as SiO2 or Si3N4 owing primarily to their pinhole-free nature. However, ion plating and sputtering are useful for decorative coatings. Thus the combination of the above-mentioned three processes gives us a tool to cover a wide selection of coating materials and their properties. Our multiple and continuous coating process thus provides numerous opportunities for creating new surface functions for stainless steels.

Surface modification of stainless steel in coil by an in-line dry coating process

Abstract Dry coating technologies have been widely used in the field of semiconductors and electronics. However, the technologies are rarely applied to coating or treating steel surfaces. Basic types of research have been conducted, particularly on the coating materials and processes for several years. Based on the results, a new coil-coating pilot facility using three coating processes (ion plating, sputtering, plasma chemical vapor deposition (CVD)) in tandem for the first time was developed and installed at the Hikari Works of the Nippon Steel Corporation. In particular, techniques connecting the three different processes for continuous operation were developed, and the optimum coating conditions were established for corrosion resistance, decorativity and electrical insulation. The development of a differential pressure chamber enabled connection of the three coating processes with different operating pressures on a single continuous line. This in-line dry coating process can be used not only for single-layer films (TiN, SiO x etc.) but also for multiple-layer films. Thus, it meets a great variety of market needs. In this paper, the deposition of TiN and TiC coatings by ion plating, Al x O y and chromium coatings by sputtering, and SiO x coatings by plasma CVD onto stainless steel sheet in coil will be introduced, together with the results of thickness uniformity, adhesivity, corrosion resistance and other properties for general applications and the results of electrical resistance for application as insulators. Decorative TiN coatings deposited onto bright annealed stainless steel by ion plating should be uniform in thickness with a gold color. These coatings also give excellent abrasion resistance. SiO x coatings deposited onto bright annealed surfaces of TP430 stainless steel by plasma CVD have excellent corrosion resistance against Cl - attack, to the degree of uncoated TP304 BA. Al x O y coatings on bright annealed stainless steel formed by sputtering give rise to an interference color. Al x O y coatings possess high electrical resistance which amounts to over 1 MΩ with the optimization of r.f. power and reduction in substrate surface defects. Thus, the new in-line dry-coating process is capable of coating a variety of materials onto stainless steel sheet in coil, and also of producing highly functional steel surfaces.

Technical note: Development of corrosion-resistant decorative colored stainless steel coils by an in-line dry-coating process

Summary Dry-coating technologies have been widely used in the field of semiconductors and electronics. However, the technologies are rarely applied to coat or treat steel surfaces. Basic types of research have been conducted, particularly on the coating materials and process for several years. Based on the results, a new coil-coating pilot facility using three coating processes (ion plating, sputtering, plasma chemical vapor deposition (CVD)) in tandem for the first time was developed and installed at the Hikari Works of Nippon Steel Corporation. In particular, technologies to connect the three different processes for continuous operation were developed, and the optimum coating treatment was established for corrosion resistance and decorative color. The develop ment of the differential vacuum chamber enabled the connection of the three coating processes with different vacuum pressures on a single continuous line. This in-line dry-coating process can be utilized to apply not only single-layer films (TiN, SiO x etc.) but also multiple-layer films. Thus, it meets a great variety of market needs. In this paper, the deposition of TiN and TiC films by ion plating, Al 2 O 3 and chromium films by sputtering and SiO. films by plasma CVD on stainless steel sheet in coil form will be introduced, together with the results of thickness uniformity, adhesivity, corrosion resistance and other properties. Decorative TiN coatings on bright annealed surfaces of type 304 stainless steel by ion plating should be uniform in thickness with a gold color, the tone of which can be easily tuned by varying the ratio of the titanium nitrogen composition. It also gives excellent abrasion resistance. SiO x coatings on bright annealed surfaces of type 430 stainless steel by plasma CVD have excellent corrosion resistance against CI − attack, to the degree of uncoated type 304 BA. They also have outstanding electrical resistance for use as an insulating film. Al 2 O 3 coatings on BA surfaces of type 304 stainless steel formed by sputtering give rise to an interference color, so that any desired color from blue to pink can be obtained by changing the thickness of the coating. Al 2 O 3 films possess not only high electrical resistance but also high radiant capability for far-IR radiation. Thus, a new in-line dry-coating process is capable of coating a variety of materials on stainless steel sheet in coil form, and also producing highly functional steel surfaces.