Welding of Ni-Mo-Cr Alloy (Hastelloy C)

Ni-Mc-Cr Alloy (Hastelloy C) is attracting attention in recent years, as a corrosion resistant material available for use in chemical plants and equipments. It has been necessary for us to establish techniques for production and fabrication of this alloy. We carried out experimental researches concerned with weldability, workability and heat treatment of this alloy. The results obtained are summarized as follows; 1. As decrease of alongation in hot-shortness range from 500°C is not heavy, it is expected that the welding crack sensitivity will not be an important problem on this alloy. 2. The precipitation takes place in temperature range from 600°C to 1150°C, and it becomes most pronounced at 800°C and 900°C. 3. Work-hardening properties of this alloy are clarified, and the allowable limit of cold working ratio is estimated 20% in mother metals and 10% in weld metals. 4. By using inert gas shielded-tungsten arc welding process, sound welds from anycracks or porosities can be obtained without difficulty. However, to prevent precipitation and grain growth, it must be noted, that the weldments have to be cooled as fast as posible. 5. In case of an overlay welding on mild steel plates, effects of dilution extend to the third layer. 6. This alloy should be solution heat-treated by holding at temperature from 1200°C to 1250°C, and then cooled rapidly in water or air.