The reason why nickel alloys are very popular in the welding world is because of their resistance to corrosion as well as their high temperature properties. This makes them very e effective when put to work in extreme temperatures. During the welding process, it is important to ensure that the properties in nickel alloys are maintained across the weld zone. The idea is to have the weld being of good quality and without flaws. Considering their many applications, welds from nickel alloys should be fit for their intended purposes. Ordinarily, how well nickel alloy equipment performs when subjected to corrosive environments is subject to care taken by welders. Having a high-quality weld is the single-most important objective. To achieve this quality, there are several factors that require absolute attention during fabrication.
Alloying Pure Nickel
One of the main reasons why nickel is alloyed is to increase its range of properties that can be achieved with other metals. Such nickel alloys can range from; nickel aluminum bronze, copper nickel alloy 70 30, nickel alloy steel, nickel 400, nickel 405, nickel 500 and nickel 718 alloys. Alloying of nickel can be categorized into two major groups. The first group consists of alloys that are solid-solution strengthened such as Nickel Iron Chromium and Nickel Copper. One of the unique characteristics of these alloys is that they are not hardened by heat treatment since they do not undergo any phase change during welding. The other group of alloys is one that consists of alloys that undergo precipitation hardening. Some of the alloys in this group include an alloy consisting of nickel, iron and chromium. Ordinarily, an alloy is more complex and has enhanced mechanical properties. For a perfect weld, it is important that the right filler metal is used during the fabrication. There should also be a post-weld heat treatment process in order to achieve the right properties on the weld zone. You can use most fusion welding process on nickel alloys such as copper nickel alloy 70 30. What is important to understand is that alloys such as copper nickel alloy 70 30 suffer from hot cracking or solidification which is why modest heat inputs is recommended to prevent cracking.
Importance of Cleanliness
During the welding of nickel alloys such as copper nickel alloy 70 30, cleanliness is very important considering that contamination from sulphur, bismuth and phosphorous is ever-present in machining products, greases and oils. The presence of such contaminants can cause solidification cracking. Cleaning involves removing oxides from the weld-surface. Removing oxides from the weld-zone is difficult going by how adherent these oxides are. The oxides can be removed from the weld surface through abrasive grinding or machining. Wire brushing is not recommended as a cleaning method as it can polish the oxide as opposed to removing it entirely. When the oxides are not removed from the surface of the alloy, there is the possibility that it may not melt during subsequent welding leading to lack of fusion-oxides have a higher melting point. The tools used are supposed to be suitable and applicable to nickel alloys such as copper nickel alloy 70 30.
