Trends of thermal spraying technology in Japanese steel industry is summarized by investigating the patent applications filed in Japan Patent Office in the past 20 years from FY1990 to FY2009. The total number of patents filed in 8 Patent Offices (Japan, United States, Europe, China, Korea, Russia, Brazil and India), retrieved by the International Patent Classification symbol C23C4/00 (IPC index key: Coating by spraying the coating material in the molten state ), is 15,082. The ratio of patent applications filed in each Patent Office is as follows: JP (39%), US (22%), EP (17%), CN (9%), KR (6%), RU (3%), BR (3%) and IN (1%). The database used in this study is from commercially available “PatBase”. Number of patent applications of thermal spray technology (C23C4/00) in Japan is 4,369. Among these patents, the ratio of patents related to steel industry filed by major Japanese steel companies is 13% of total patents of every industrial segment in Japan. These patents are classified according to (1) coating applications in the process of steel production lines, (2) performances and effects obtained by coatings, .and (3) coating materials. In this paper, current status and future trend of thermal spray technology in Japanese steel industry is discussed.

Up to now no coating systems are marketable in the field of direct hot extrusion, which provide both surface protection of the parts being in contact to the billet (i.e. container and die), and a significant reduction of the frictional losses being induced by the billet passing along the container walls. To dispense the use of lubricants and to enhance the usable forming capacity of the process, different oxide ceramics were given in one suspension and plasma sprayed. The aim is to reach a mixing of the feedstock to obtain deterministic solid solutions of the oxide phases which show a reduction of their coefficient of friction under dry sliding conditions. To reach this goal the high surface-to-volume ratio of feedstock with primary particle sizes below 100 nm was used. By means of X-ray diffraction it could be proven, that the desired phases could be synthesized. The coatings showed a considerable lowering of their frictional coefficient in tribological testings against 100Cr6 in the region of the operation temperatures for the hot extrusion of aluminium alloys. Besides the experimental work the fundamentals of the mixing process of different oxides regarding crystallographic aspects are discussed.

Low-pressure cold spraying (LPCS) is a coating technique, in which a portable cold spray system, e.g., DYMET 304K system is used to prepare technical coatings. Usually, compressed air is used as the process gas. The LPCS process is an appropriate method for spraying of metallic-ceramic composite powder materials, e.g., Cu, Ni, Zn, Al with additions of Al 2 O 3 particles in the powder blends. The main functions of the hard ceramic particles are cleaning the nozzle, activating the sprayed surface and peening the coating structure. This method has advantages for example in the field of repairing and restoration applications. For that, repairing casting defects and voids is one interesting application of the process. For these purposes, zinc-based composite materials are recommended for restoration and repairing of corrosion and mechanical damages. In this study, Zn+Al+Al 2 O 3 , Zn+Cu+Al 2 O 3 and Zn+Ni+Al 2 O 3 composite materials were investigated. Zinc and aluminum give corrosion resistance by cathodic protection whereas copper and nickel will provide also more mechanical resistance. Coating properties, such as microstructures, open-cell potential behavior and mechanical properties (hardness and adhesion strength) were investigated. The coatings have relatively dense coating structures and for corrosion resistance, zinc gives a cathodic protection for other materials in these composite coatings. Furthermore, mechanical properties are sufficient due to the relatively high hardness and adhesion to the Fe52 steel base material. These coatings have high potential in their use as repair materials for macroscopic casting defects.

Agglomerate sintered and blended NiCrAlY-Y 2 O 3 cermets were prepared from NiCrAlY and Y 2 O 3 powders by two process routes. The particle morphologies and powder characteristics of both cermets feedstock using for thermal spraying were investigated. Both types of NiCrAlY-Y 2 O 3 cermets and one commercial CoCrAlY-Y 2 O 3 cermets were HVOF thermal sprayed onto the stainless steel substrate to obtain coatings having a thickness about 100 microns. Porosity and thermal shock resistance of coatings were examined. Four thermal sprayed coatings were comparatively evaluated build-up resistance by contacting reaction with MnO, Fe 3 O 4 powders and manganese bearing carbon steel statically at high temperatures. The agglomerate sintered NiCrAlY-Y 2 O 3 coatings have good resistance to manganese oxide build-up but bad resistance to iron oxide build-up. The agglomerate sintered cermets coating has better build-up resistance than blended cermets coating.