PENGARUH DURASI PADA PROSES SHOT PEENING TERHADAP SIFAT FISIS, MEKANIS, WETTABILITY DAN KETAHANAN KOROSI SUMURAN MATERIAL STAINLESS STEEL 316L

MUHAMMAD RIFQI, Dr. Eng. Priyo Tri Iswanto, S.T., M.Eng.

2017 | Skripsi | S1 TEKNIK MESIN

Stainless steel 316L merupakan jenis material yang umumnya digunakan dalam implant tulang. Stainless steel 316L perlu ditingkatkan sifat fisis, mekanis, wettability dan ketahanan korosi sumuran sehingga dapat digunakan dengan aman. Austentic steel tidak dapat menggunakan perlakuan panas sehingga digunakan perlakuan dingin, yaitu shot peening. Shot peening adalah metode perlakuan dingin untuk meningkatkan sifat material dengan penembakan bola baja ke permukaan material. Penelitian ini bertujuan untuk menganalisis pengaruh shot peening terhadap kekasaran permukaan, struktur mikro, kekerasan, wettability dan ketahanan korosi sumuran pada stainless steel 316L. Proses shot peening dilakukan pada permukaan spesimen stainless steel 316L dengan durasi penembakan 1, 2, 4, 30, 40, 50, dan 60 menit, menggunakan steel ball diameter 0,6 mm dengan kekerasan 40-50 HRc, tekanan kompresor dijaga konstan pada 8 bar dengan diameter nozzle 5 mm, dan jarak tembak antara nozzle dengan permukaan spesimen 6 cm. Spesimen hasil perlakuan dan raw material diuji nilai kekasaran permukaan, kekerasan permukaan, distribusi kekerasan, wettability, laju korosi dan uji struktur mikro. Pengujian wettability dilakukan dengan meneteskan air ke atas permukaan spesimen hasil shot peening dan raw material stainless steel 316L dan pengujian korosi menggunakan metode cyclic polarization. Hasil penelitian menunjukkan bahwa proses shot peening dapat merubah kekasaran permukaan hingga titik optimum dan apabila durasi shot peening diperpanjang maka akan terjadi sedikit peningkatan nilai kekasaran permukaan. Selain itu, shot peening juga mengubah struktur mikro, meningkatkan kekerasan material serta menyebabkan perubahan sifat pada stainless steel 316L dari hydrophobic menjadi hydrophilic. Proses shot peening meningkatkan ketahanan terhadap korosi sumuran namun pada titik tertentu terjadi kerusakan pada lapisan pelindung sehingga laju korosi naik dan akan turun dengan memperpanjang durasi shot peening. Shot peening dengan durasi penembakan 1 menit dapat dipakai menjadi acuan untuk meningkatkan sifat permukaan yang dimana memiliki kekasaran permukaan sebesar 2 μm yang bersifat hydrophilic, kekerasan permukaan sebesar 330.71 kgf/mm2 dan ketahanan terhadap korosi sumuran yang baik.

316L stainless steel is a material that is commonly used for implants. In order for this material to be used safely, improvements need to be done. These improvements include physical properties, mechanical properties, wettability and pitting corrosion resistance. Austenic steel cannot be treated by heat therefore cold treatment is used, in this case; shot peening. Shot peening is a cold treatment method used to increase material properties by shooting steel balls onto the material’s surface. The purpose of this study is to analyse the effect of shot peening towards the surface roughness, microstructure, hardness, wettability and corrosion resistance of 316L stainless steel.The shot peening process is performed on the surface of 316L stainless steel specimens with a peening duration of 1, 2, 30, 40, 50, and 60 minutes using 0.6 mm diameter steel balls with the hardness of 40-50 HRc. Compressor pressure is kept constant at 8 bar with a nozzle diameter of 5 mm, and a peening distance of 6 cm between the nozzle and specimen. Treated and raw specimens are tested for surface roughness, surface hardness, hardness distribution, wettability, corrosion rate and microstructure. The wettability test is conducted by dripping water on to the surface of the shot peened and raw specimens, whereas the corrosion test is performed by cyclic polarization method. Results show that the shot peening process can enhance the surface roughness to the optimum point and if the duration of shot peening is extended, a slight increase in surface roughness will occur. In addition, shot peening also modifies the microstructure, increases material hardness, and results in the change of property of 316L stainless steel from hydrophobic to hydrophilic. Shot peening process increases the resistance to pitting corrosion, however at a certain point, damages the protective layer resulting in the increase of corrosion rate. This rate can be decreased by extending the duration of shot peening. One minute of this treatment can be used as a reference to improve surface properties which has a hydrophilic 2 μm surface roughness, surface hardness of 330.71 kgf / mm2 and good corrosion resistance.

Kata Kunci : durasi shot peening, stainless steel 316L, kekasaran permukaan, Kekerasan, struktur mikro, wettability, korosi sumuran