Abstract
The microstructures and hardness of tungsten inert gas (TIG) welded experimental 57Fe15Cr25Ni steel were investigated through optical–scanning electron microscopy analyses and with a hardness tester, respectively. The welding process restructured the constituent atoms into regular and irregular crystal lattices. Rapid cooling of the weld metal allowed the formation of a dendritic (columnar) structure, with porous grains. By contrast, slow cooling influenced HAZ and led to the formation of grain structures. The crystal lattice became more organized and larger than other zones. Meanwhile, the base metal formed circular nets that covered large area inside thick and thin grain boundaries. The diffraction patterns revealed texturing in the weld metal. The crystallite orientation changed from (111) to (200) and (220) planes. The weld metal profile broadened (amorphous) and had full width at half maximum (fwhm) value larger than those in HAZ and the base metal. The weld metal possessed hardness of 121 HV, which is slightly lower than the hardness of the base metal (130 HV). HAZ exhibited the highest hardness value (152 HV). Hardening was influenced by carbon and outer oxygen migration to the grain boundaries, which formed colonies, i.e., chromium carbide, aluminum carbide, aluminum oxide, silicone oxide, and silicon carbide (precipitation hardening). Welding (heat) may change the microstructure and hardness of HAZ and the weld metal region, which would be brittle and very critical in responding to applied loads.
Bahasa Abstract
Struktur Mikro dan Kekerasan pada Las TIG Baja Experimental 57Fe15Cr25Ni. Pengamatan pengaruh panas las pada pembentukan struktur mikro dan kekerasan plat baja 57Fe15Cr25Ni menggunakan mikroskop optik (OM) - electron (SEM), dan Microhardness Vickers Testing Machine yang beridenter diamond telah dilakukan. Hasil memperlihatkan bahwa mekanisme panas las mampu mempengaruhi proses penataan ulang atom-atom penyusun kisi kristal menjadi teratur dan tidak teratur. Karena mengalami pendinginan yang cepat, struktur mikro pusat las (weld metal) berbentuk dendrit columnar berpori dalam lingkupan struktur matriks, sedang efek pendinginan melambat di daerah HAZ mengakibatkan penyusunan kisi kristal menjadi lebih teratur dan berukuran lebih besar daripada ukuran butir matrik. Di daerah logam matrik (base metal) struktur mikro berbentuk jejaring melingkar besar dan kecil yang dilingkupi batas butir (grain boundary) tebal dan tipis. Texturing terdeteksi di daerah pusat las. Kristal mengubah orientasi dari bidang refleksi (111) ke bidang refleksi (200) dan (220). Profil pusat las melebar (amorf), menyebabkan angka lebar setengah puncak maksimum (fwhm) lebih besar dari pada daerah HAZ dan basemetal, dan sangat sesuai dengan pengamatan struktur mikro permukaan bahan. Nilai rerata kekerasan pada daerah weld metal sekitar 121 HV, lebih rendah daripada daerah base metal sekitar 130 HV, sedang daerah HAZ memiliki nilai rerata kekerasan yang paling tinggi sekitar 152 HV. Pengerasan ini juga dipengaruhi oleh migrasi carbon dan oxygen luar ke batas butir (precipitation hardening) dan membentuk koloni seperti: chrom carbide, aluminum carbide, aluminum oxide, silicone oxide and silicon carbide. Disimpulkan bahwa panas las dapat mempengaruhi pembentukan struktur mikro dan sifat mekanik (kekerasan) bahan di daerah HAZ dan inti lasan. Kedua daerah ini dapat menjadi rapuh (brittle) dan sangat kritis dalam merespon beban terpakai.
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Recommended Citation
Parikin, Parikin; Dani, Mohammad; Rivai, Abu Khalid; Ismoyo, Agus Hadi; Iskandar, Riza; and Dimyati, Arbi
(2018)
"Microstructures and Hardness of TIG Welded Experimental 57Fe15Cr25Ni Steel,"
Makara Journal of Technology: Vol. 22:
Iss.
2, Article 2.
DOI: 10.7454/mst.v22i2.3430
Available at:
https://scholarhub.ui.ac.id/mjt/vol22/iss2/2
Included in
Chemical Engineering Commons, Civil Engineering Commons, Computer Engineering Commons, Electrical and Electronics Commons, Metallurgy Commons, Ocean Engineering Commons, Structural Engineering Commons
