Measurements of residual stress on the 57Fe25Cr15Ni steel plate with no-filler TIG-welding process were carried out. This work was conducted to determine the nature of weld ability in synthesized steel. The bulks were formed in a dimension of 30x20x7 mm 3 to ease data retrieval. Results show that the largest residual stress occurred in the weld metal area, amounting to 82.40 MPa with lattice stretching of 0.18%. Conversely, the values decreased to 65.92 MPa and a stretch of 0.14% in the HAZ area. This residual stress is a tensile stress that can reduce the mechanical strength of the material since it adds to the applied loads. This was confirmed by microstructure observations. The carbon content was very high in the dark lines. Weaken materials usually start from this side and could initiate the intergranular cracks that rapidly migrate among its grain boundaries. Abstrak Pengukuran Tegangan Sisa pada Sambungan Las-TIG Bahan Struktur Baja Austenitik 57Fe15Cr25NiMenggunakan Teknik Difraksi Sinar-X. Pengukuran tegangan sisa pada pelat baja 57Fe15Cr25Ni akibat proses pengelasan TIG tanpa filler telah dilakukan. Pekerjaan ini dilakukan untuk mengetahui sifat mampu las dari bahan pelat baja. Bahan 'bulk' dibentuk plat dengan dimensi 30x20x7 mm3 untuk memudahkan pengambilan data. Hasil penelitian menunjukkan bahwa tegangan sisa terbesar terjadi di daerah pusat las, sekitar 82,40 MPa dengan kisi peregangan 0,18% dan turun pada sekitar 65,92 MPa dengan regangan sebesar 0,14% di daerah HAZ. Tegangan sisa ini adalah tegangan tarik yang dapat mengurangi kekuatan mekanik material karena mampu menambah beban terpakai. Hal ini ditegaskan dengan pengamatan mikrostruktur. Kandungan karbon sangat tinggi di garis hitam. Pelemahan bahan biasanya dimulai dari sisi ini dan bisa mengawali retakan intergranular, yang dengan cepat dapat bermigrasi di antara batas butirnya.

The residual stress measurements around weld-joint of ZrNbMoGe alloy have been carried out by using X-ray diffraction technique in PTBIN-BATAN. The research was performed to investigate the structure of a cladding material with high temperature corrosion resistance and good weldability. The equivalent composition of the specimens (in %wt.) was 97.5%Zr1%Nb1%Mo½%Ge. Welding was carried out by using TIG (tungsten inert gas) technique that completed butt-joint with a current 20 amperes. Three region tests were taken in specimen while diffraction scanning, While diffraction scanning, tests were performed on three regions, i.e., the weldcore, the heat-affected zone (HAZ) and the base metal. The reference region was determined at the base metal to be compared with other regions of the specimen, in obtaining refinement structure parameters. Base metal, HAZ and weldcore were diffracted by X-ray, and lattice strain changes were calculated by using Rietveld analysis program. The results show that while the quantity of minor phases tend to increase in the direction from the base metal to the HAZ and to the weldcore, the quantity of the ZrGe phase in the HAZ is less than the quantity of the ZrMo2 phase due to tGe element evaporation. The residual stress behavior in the material shows that minor phases, i.e., Zr 3 Ge and ZrMo 2 , are more dominant than the Zr matrix. The Zr 3 Ge and ZrMo 2 experienced sharp straining, while the Zr phase was weak-lined from HAZ to weldcore. The hydrostatic residual stress (σ) in around weld-joint of ZrNbMoGe alloy is compressive stress which has minimum value at about -2.73 GPa in weldcore region.

Abstract. Surface treatment by implantation with nitrogen-ion was performed on the commercial feritic high strength steel AISI 410 which is termed for high temperature applications. The aim of this research was focused on the surface modification to improve its high temperature oxidation property in the early stages. Ion implantation was carried out at acceleration energy of 100 KeV and ion current 10 mA for 30, 60 and 90 minutes. The samples were subjected to the high temperature oxidation test by means of thermogravimetry in a magnetic suspension balance (MSB) at 500 o C for 5 hours. The scanning electron microscopy (SEM), Xray diffraction spectrometry (XRD) and Vickers Hardness measurement were used for sample characterization. The formation of ferro-nitride phase after implantation did not occur, however a thin layer considered to contain nitrogen interstitials was detected. The oxidation of both samples before and after implantation followed parabolic kinetics indicating inward growth of oxide scale characteristically due to diffusion of oxygen anions towards matrix surface. After oxidation test relativelly stable oxide scales were observed. Oxidation rates decreased proportionally with the increasing of implantation time due to the formation of oxide layer which is considered to be effectiv inhibitor for the oxygen diffusion.

PENGUKURAN TEGANGAN SISA PLAT BAJA STRUKTUR NON STANDAR A-2 ROL PANAS DENGAN TEKNIK DIFRAKSI NEUTRON. Pengukuran tegangan sisa bahan struktur plat baja austenitiik (A-2) (FeCrNi) hasil mekanisasi rol panas telah dilakukan di PTBIN- BATAN. Studi ini dilatarbelakangi oleh pemanfaatan proses pengerolan pada komponen bahan struktur konstruksi yang sangat diminati karena menawarkan rasio kekuatan beban sangat baik, dan dalam rangka penerapan bahan viral yang memerlukan persyaratan khusus ketika faktor keselamatan menjadi prioritas utama. Empat buah specimen disiapkan dalam kegiatan ini; satu sebagai bahan referensi yang tidak dirol (A2D0n), dan tiga buah specimen lain (A2D2n, A2D3n dan A2D5n) diberi perlakuan rol panas dengan kuantitas reduksi berbeda, yakni: 71%, 81% dan 87%. Hasil memperlihatkan bahwa: pengerolan hingga reduksi 71% membangkitkan peregangan kisi sebesar 0.25% dan tegangan sisa tarik sebesar 9,7 MPa sedangkan peregangan kisi sebesar 0,27% dan tegangan sisa terbesar 10,2 MPa terjadi pada reduksi 81%. Selanjumya peregangan kisi dan tegangan sisa meluruh kembali bertururan hingga 0,23% dan 8,3 MPa terjadi pada reduksi pengerolan panas sebesar 87%. Disimpulkan bahwa: peningkatan peregangan baban baja austenitik-2 terjadi akibat pergeseran bidang-bidang kristal (slip plane) oleh mekanisme pengerolan yang mampu meningkatkan kekuatan mekanik bahan berupa pengerasan regangan (strain hardening), dan fenomena kecenderungan distribusi tegangan sisa bahan struktur auslenitik-2 adalah tegangan tarik (tensile stress).Kata Kunci : plat baja FeCrNi, rol panas, tegangan sisa, difraksi neutron.