Is Inconel harder than steel?

Inconel
Inconel is the trade name of a series of nickel-chromium high-temperature alloys produced by Specialty Metals. It is extremely resistant to extreme temperatures and can withstand approximately 2,000°F (depending on alloy) without loss of strength. It also performs well at low temperatures.

In addition to extreme temperature properties, Inconel has excellent mechanical properties at room temperature. For example, Inconel 725 has a tensile strength of up to 180 ksi, which is twice the strength of structural steel. Some Inconel alloys, such as Inconel 718, are precipitation hardened, which further increases their strength. Inconel is also highly resistant to corrosion, including oxidation, pitting, crevice corrosion and corrosion cracking.

The properties of Inconel make it a valuable metal for use in the most demanding conditions. However, like most superalloys, it is much more expensive than common metals such as steel, aluminum and titanium.

Machining Inconel
The strength of Inconel makes it a valuable material for use in extreme conditions, but it also makes it difficult to machine. It is very hard and prone to work hardening during machining, which can damage cutting tools and deform the workpiece.

Stress-relieving Inconel through pre-machining solution treatment helps reduce surface hardness and limit work hardening, thereby reducing tool stress and wear. Ceramic cutting tools are recommended because of their ability to make fast, continuous cuts that minimize work hardening. It is also important to avoid pecking, which increases work hardening.

Welding Inconel
Most Inconel alloys are difficult to weld because the welds break easily. However, some Inconel alloys are designed to be weldable. These are typically TIG (tungsten inert gas) welded and use Inconel 625 (the easiest to weld Inconel alloy) as the filler metal. While TIG welding typically does not require filler, it is recommended for Inconel welding because it is very difficult to fuse two parts without cracking.

Inconel applications
Due to its high chemical and high temperature resistance, Inconel is well suited for a variety of aerospace, oil and gas, and marine applications. Some common use cases for Inconel include:

Jet engine exhaust.
Turbine.
Exhaust pipe connector.
Stack of flares.
Natural Gas Pipeline.
Marine propeller blades.
Aerospace and marine fasteners.
Heavy machinery parts.
Inconel is an ideal material when extreme temperatures and corrosion resistance are required, especially when high temperatures would reduce the strength and oxidation resistance of other metals.

titanium
Titanium is an elemental metal with an extremely high strength-to-weight ratio, making it useful for applications such as aerospace structural components where weight reduction is critical. Titanium is about as strong as steel but only half the weight. However, these properties do come with a higher price tag than more common metals like aluminum and steel, although it is generally much cheaper than Inconel.

Titanium does not react with oxygen and water at ambient temperatures. Like Inconel, titanium forms a passivating oxide layer on its surface to protect the material. This makes titanium extremely corrosion-resistant, even resistant to strong acids such as sulfuric and hydrochloric acid. Additionally, titanium is biocompatible and non-toxic, allowing it to be used in many medical applications.

Titanium is available in two grades: commercial pure titanium and alloy titanium. The most common alloy is Ti 6Al-4V, which is alloyed with aluminum and vanadium and accounts for about half of the total titanium used worldwide. This and other titanium alloys are designed to be harder, stronger and/or easier to machine than pure titanium. Commercially pure (CP) titanium is softer and more ductile than titanium alloys, but its corrosion resistance is outstanding.