Date

2018

Author

Çakmak, Hafize

Metadata

Show full item record

Item Usage Stats

106
views

54
downloads

Cite This

In the industrial applications, surface modification/treatment techniques give preference to reach the better service life for components which encounter the problem of wear. In practice, worn components either have to be rejected or rebuilt by employing various surface treatment applications which actually do not only improve the wear resistant of the surface, but also it helps preserve against corrosion and oxidation problems at higher temperature. Among these industrial coating & surface treatment applications, hardfacing is a more conventional surface treatment technique, which is implemented by welding, to grade up the surface specialty of the base/substrate metals. In this coating application, the production of a new surface layer will be accomplished by homogeneous deposition of an alloy onto the surface of a relatively cheap conventional base/substrate metal by welding so as to obtain an enduring surface layer which has impact and wear resistance ability, erosion and corrosion resistance or any integration of these factors. Hence, the coating alloys should have some desired properties correspondingly, such as high hardness, demanded abrasion resistance/tribological properties, specific corrosion and heat resistance. On the other hand, bulk amorphous steels (BASs) have promising future due to their superior mechanical and physical properties compared with their crystalline states. BASs display very high hardness, Young’s modulus, wear and corrosion resistance due to their amorphous nature. This nature of the BAS is lack of any crystallographic defects such as grain boundaries and dislocations which provides better corrosion resistance and mechanical properties. These unique characteristics make the BASs a potential candidate for coating applications. In this respect, the purpose of the thesis is to develop and make use of a new alternative coating material based on BAS in place of traditional coating materials which will be utilized in industrial coating and surface treatment implementations by hardfacing. For this application, the BASs were re-synthesized from cast iron scraps, which was derived from NOVALAB’s theoretical approach in order to improve the glass forming ability of iron-based metallic glasses, by arc melting under controlled atmosphere. Suction casting technique has been employed for the direct production of 3 mm in diameter BAS rod, subsequently utilized as a filler material in TIG welding process. Hardfacing application was applied on relatively cheap low/medium carbon steel (S275) and stainless (304) steel substrates. Coating quality, its coherency and conformity were examined in two different cooling environments. It was observed that owing to high bulk glass forming ability (BGFA), BAS coating material preserved their amorphous structure with extreme high hardness, 3-4 times higher than the substrate metal and displayed good wear/abrasion and corrosion resistance in various extreme environments.

Subject Keywords

Steel alloys., Coating processes., Surfaces (Technology)., Amorphous substances.

URI

http://etd.lib.metu.edu.tr/upload/12622229/index.pdf
https://hdl.handle.net/11511/27486

Collections

Graduate School of Natural and Applied Sciences, Thesis