Inconel: another heat-resistant superalloy (HRSA), Inconel is the best choice for extreme temperatures or corrosive environments. In addition to jet engines, Inconel 625 and its harder and stronger brother Inconel 718 are also used in nuclear power plants, oil and gas drilling platforms, chemical processing facilities, etc. Both are quite weldable, but they are expensive and even more difficult to process than CoCr. Therefore, they should be avoided unless necessary.
Stainless steel: by adding the minimum 10.5% chromium, the carbon content is reduced to the maximum 1.2%, and adding alloy elements such as nickel and molybdenum, the metallurgist converts ordinary rusty steel into stainless steel, which is the killer of anti-corrosion switch in the manufacturing industry. However, because there are dozens of levels and categories to choose from, it may be difficult to determine which is best for a given application. For example, the crystal structure of austenitic stainless steels 304 and 316L makes them non-magnetic, non hardenable, ductile and quite ductile. On the other hand, martensitic stainless steel (grade 420 is grade 1) is magnetic and hardenable, making it an ideal choice for surgical instruments and various wear-resistant parts. There are also ferritic stainless steel (mostly 400 Series), duplex steel (think of oil and natural gas), and precipitation hardening stainless steel 15-5 pH and 17-4 PH, all of which are favored for their excellent mechanical properties. Machinability ranges from fairly good (416 stainless steel) to moderately poor (347 stainless steel).
Steel: like stainless steel, there are too many alloys and properties. However, four important issues to be considered are:
1. The cost of steel is usually lower than that of stainless steel and high-temperature alloy
2. In the presence of air and moisture, all steel will corrode
3. Except for some tool steels, most steels have good machinability
4. The lower the carbon content, the lower the hardness of the steel (represented by the first two digits of the alloy, such as 1018, 4340 or 8620). That is, steel and its close relatives iron are by far the most commonly used of all metals, followed by aluminum.
The list does not mention the red metals copper, brass and bronze, or titanium, another super important superalloy. There is also no mention of some polymers. For example, ABS is the material of Lego building blocks and drainage pipes, which can be molded and processed, and has excellent toughness and impact resistance.
Engineering grade plastic acetal is a remarkable example, applicable to all products from gears to sporting goods. The combination of strength and flexibility of nylon has replaced silk as the preferred material for parachutes. There are also polycarbonate, polyvinyl chloride (PVC), high density and low density polyethylene. The key is that the selection of materials is extensive, so as a part designer, it is meaningful to explore what is available, what is good, and how to process. Quick plus offers more than 40 different grades of plastic and metal materials.
