1. Tungsten (1960–2450 MPa)
Tungsten is one of the hardest metals you will find in nature. Also known as Wolfram, the rare chemical element exhibits a high density (19.25 g/cm3) as well as a high melting point (3422 °C/ 6192 °F). In its rare form, tungsten is hard to work with due to its brittleness, which can be changed when turned pure. Tungsten is often utilized to create hard alloys, such as high speed steel, to increase protection against abrasion as well as improve electrical conductivity.
2. Iridium (1670 MPa)
Like Tungsten, Iridium is a chemical element that shows signs of high density and a tolerance of high temperatures. Iridium belongs to the platinum group of metals, resembling platinum in its look. However, iridium is hard to work with. Since it is very hard, iridium is also quite brittle, which is only aggravated by its very high melting point of over 2,000 °C. Iridium ranks among one of the rarest Elements on Earth’s surface, as well as one of the most corrosion-resistant elements.
Steel is an alloy metal made of iron and other elements, such as carbon. It is the most used material in construction, mechanical engineering, and other industries. Due to the many variations and levels of quality steel can adopt, there is no uniform hardness value. There exist many techniques of tempering steel to improve the wear protection of steel, heat tolerance and protection against abrasion. Borocoat for example, optimizes the hardness of steel without making it brittle.
4. Osmium (3920–4000 MPa)
Osmium belongs to the platinum group metals and displays a high density. In fact, it is the densest, naturally occurring element on Earth with 22.59 g/cm3. This is also why Osmium does not melt until 3033 °C, a temperature that makes it difficult to work with the metal. When it is alloyed with other platinum group metals (such as iridium, platinum and palladium) it can be used in many different areas where hardness and durability are needed.
5. Chromium (687-6500 MPa)
Chromium is an element often found in alloys, such as stainless steel. On the Mohs scale, which measures scratch resistance, it is found among the top. Chromium is valued for its high corrosion resistance as well as its hardness. Since it is easier to handle as well as more abundant than platinum group metals, chromium is a popular element used in alloys.
6. Titanium (716 – 2770 MPa)
Titanium is known for its strength. While it does not quite compare to other any other metal on this list in terms of Brinell Hardness, titanium has an impressive strength to weight ratio. Even in its pure form, titanium is harder than many steel forms. As a refractory metal, it is highly resistant to heat and abrasion, which is why titanium and its alloys are popular. It can be alloyed with iron and carbon, for example.
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