DLC 코팅된 GCV 소재의 마모 특성에 관한 연구

Abstract

Compacted graphite iron, also known as vermicular graphite iron, is a metal which is gaining popularity in applications that require either greater strength, or lower weight than cast iron. The graphite in compacted graphite iron differs in structure from that in gray iron because the graphite particles are shorter and thicker. This results in stronger adhesion between the graphite and the iron giving the material a greater tensile strength. The first commercial application for compacted graphite iron was for the brake discs for high speed rail trains. More recently compacted graphite iron has been used for diesel engine blocks. It has proven to be useful in the manufacture of V topology diesel engines where the loading on the block is very high between the cylinder banks, and for heavy goods vehicles which use diesel engines with high combustion pressures. It is also used for turbo housings and exhaust manifolds in the latter case to reduce corrosion. Diamond-like carbon (DLC) exists in seven different forms of amorphous carbon materials that display some of the unique properties of diamond. They are usually applied as coatings to other materials that could benefit from some of those properties. All seven contain significant amounts of sp3 hybridized carbon atoms. The reason that there are different types is that even diamond can be found in two crystalline poly types. The usual one has its carbon atoms arranged in a cubic lattice, while the very rare one (lonsdaleite) has a hexagonal lattice. By mixing these poly types in various ways at the nano scale level of structure, DLC coatings can be made that at the same time are amorphous, flexible, and yet purely sp3 bonded "diamond". The hardest, strongest, and slickest is such a mixture, known as tetrahedral amorphous carbon, or ta-C. Applications of DLC typically utilize the ability of the material to reduce abrasive wear. Tooling components, such as end mills, drill bits, dies and molds often use DLC in this manner. DLC is also used in the engines of modern super sport motorcycles, Formula 1 race cars, NASCAR vehicles, and as a coating on hard-disk platters and hard-disk read heads to protect against head crashes. In this study, Graphite Compacted Vermicular (GCV) material were evaluated wear charateristics according to DLC coating and DLC synthesis. The obtained results are as follows; Microstructure of GCV340 show both the spheroidal graphite and the partial disposition graphite. It become known to excellent material that the changing size about 200 ℃ have little because of two types of microstructure. The mechanical properties of GCV 340 were tensile strength 411.5 MPa, yield strength 313.8 MPa, percentage of elonglation 2.7 and micro hardness 318 Hv. We could identify DLC by micro-RAMAN, scratch test and nano-indentation. Friction coefficient shows excellent value under 0.2 in all specimen. DLC coating of 90 min was best condition.