Analisis Multiple Repair dan Holding Time Post Weld Heat Treatment Material SA 335 Grade P91 dengan Proses Pengelasan SMAW Terhadap Nilai Kekerasan dan Metalografi

Abstract

Multiple repair processes are frequently employed in the welding industry. Increasing the frequency of repairs alters the material's microstructure and enhances its hardness. SA 335 Grade P91 materials require heat treatments, such as post-weld heat treatment, to restore their mechanical properties after welding and repair processes. This research evaluated the influence of varying the number of repairs (no repair, 2 repairs, and 3 repairs) and PWHT holding time (30 minutes and 60 minutes) on weld metallography and hardness. Metallographic analysis revealed that the Heat Affected Zone (HAZ) expands with an increasing number of repairs, with the maximum HAZ area recorded in the 3-repair spesimen (211.58 mm²). The proportion of pearlite and martensite phases increases with the number of repairs, leading to an increase in hardness. However, grain growth due to prolonged holding time during PWHT tends to decrease hardness. Hardness testing results demonstrate an increase in hardness with an increasing number of repairs, especially in the weld metal. The highest hardness was observed in the 3-repair spesimen with a 30-minute holding time (343.16 HVN), while the lowest hardness was found in the non-repair spesimen with a 60-minute holding time (316.77 HVN). Spesimens with the same numbers of repairs but a longer holding time (3-repair, 60-minute holding time) exhibited a hardness of 330.87 HVN, indicating that a longer holding time tends to decrease hardness