ผลของการอบอ่อนต่อสัณฐานและสมบัติเชิงกลของโลหะผสมนิกเกิล-ทังสเตนที่ชุบเคลือบด้วยไฟฟ้า

• 主要作者: นราศักดิ์ สันวัง
• 其他作者: ยุทธนันท์ บุญยงมณีรัตน์
• 格式: Theses and Dissertations
• 語言: Thai
• 出版: จุฬาลงกรณ์มหาวิทยาลัย 2011
• 主題: โลหะผสมนิกเกิล; ทังสะเตน; โลหะ > สมบัติทางกล; การชุบเคลือบผิวด้วยไฟฟ้า; Nickel alloys; Tungsten; Metals > Mechanical properties; Electroplating
• 在線閱讀: https://digiverse.chula.ac.th/Info/item/dc:43403
• 機構: Chulalongkorn University

The microstructure and mechanical properties of electrodeposited nanostructured nickel-tungsten (Ni-W) alloys may be influenced by elevated temperatures. In this research, 3 sets of Ni-W alloy coatings (A, B and C), which have 22, 13, and 6 at.% of W, and grain size of 3, 13, and 56 nm, respectively, were fabricated, and the evolution of their microstructure and their mechanical response following annealing at 700-11000C were investigated. With the annealing temperature of 700oC, specimen A (W 22 at.%) showed an increase of hardness from 7 GPa to 10.5 GPa owing to grain relaxation. Specimen B and C (W 13 and 6 at.%) however, showed decrement of hardness from 6 GPa to 5.2 GPa, and from 4.5 GPa to 2.1 GPa, respectively. At 900oC and 1100oC, the hardness of all specimens was reduced due to grain growth, At these stages, grain size of specimen A remained in the nano-regime, while that of B and C now fell into the micro-regime. It was also found that the wear resistance of specimen A declined after heat treatment, and grain relaxation and the dominant wear mechanisms explain the difference in wear performance observed in the as-plated and as-annealed specimens. From this work, it has been thus found that Ni-W alloys experience grain growth and development of new phases, which correspondingly affect their hardness and wear resistance. The alloys with high tungsten content (22 at.%) and nano-sized grains are found suitable for use at elevated temperatures, as they are relatively stable and show high hardness at high temperatures.