ผลของการทำไนตรายดิงแบบก๊าซ, อ่างเกลือ และพลาสมาต่อความต้านทานการกัดกร่อนของเหล็กกล้าเครื่องมือทำงานร้อน H13

• Main Author: ธนกร เลิศจิระกุล
• Other Authors: ปฐมา วิสุทธิพิทักษ์กุล
• Format: Theses and Dissertations
• Language: Thai
• Published: จุฬาลงกรณ์มหาวิทยาลัย 2013
• Subjects: อุตสาหกรรมเหล็กกล้า; การกัดกร่อนและการป้องกันการกัดกร่อน; วิศวกรรมโลหการ; Steel industry and trade; Corrosion and anti-corrosives
• Online Access: https://digiverse.chula.ac.th/Info/item/dc:42751
• Institution: Chulalongkorn University

This research aims to study the effect of corrosion resistance in hot work tool steel H13 after applying gaseous, salt bath, and plasma nitriding surface modification under the same condition as in Thai industries. It was found that H13 after treatment of gaseous (AG), salt bath (AS), and plasma (AP) nitriding had incremented in surface hardness from 709 HV0.05 to 1039, 1215, and 1410 HV0.05 respectively, which resulted from the formation of Fe2-3N on the surface. From the cross-sectional microstructure, specimens could be divided into 2 groups: the group with compound layer on the surface (AG, AS) and the group without compound layer (AP) on the surface. From the corrosion resistance tested by potentiodynamics technique in 0.9 %m/v NaCl solution under room temperature, it was found that the group with compound layer (AG, AS) had significantly decreased of corrosion potential and increased of corrosion rate compared to the H13 without nitriding (AR). The passive region could be observed in the polarization curve. The surface images after the test revealed the crevice corrosion, which corresponded to the specimens after the surface treatment that had micropores. On the other hand, the group without compound layer (AP) had slightly decreased of corrosion potential and slightly increased of corrosion rate compared to the H13. The passive region could not be identified. The surface images after the test had shown uniform corrosion. However, the potentiostatic technique test in 0.9 %m/v NaCl solution under room temperature for 5 hours 30 minutes and the potential at -300 and 0 mV which occurred only anodic reaction, revealed that the group with high corrosion resistance compound layer (AG, AS) had lower corrosion current than those without compound layer (AP).Then, the possibility of improving hardness and corrosion resistance of H13 was evaluated by added chromium electroplating and surface decarburizing processes. The groups obtained were H13 with chromium electroplating then plasma nitriding (EP), H13 with plasma nitriding then chromium electroplating (PE), H13 with decarburizing then plasma nitriding (DP), and H13 with decarburizing then plasma nitriding and then chromium electroplating (DPE). From the characterizations and discussions, it can be concluded that H13 with plasma nitriding then chromium electroplating (PE) could gain surface hardness with minimal decreased in corrosion resistance.