10 Hardest Metals

There are many ways to define hardness, but using a standard scale, it's possible to rank the relative hardness of metallic elements.

Of all the elements in the periodic table, most of them can be considered metals. In general, metals are defined as materials that are good conductors of heat and electricity, are solid at room temperature, are opaque and lustrous, and can be stretched and pounded into sheets.

What is Hardness?

The hardness of a material can be defined in different ways. In general, hardness is a material's relative resistance to indentation, but it can also mean the material's resistance to scratching, cutting or bending.

A common method of ranking the relative hardness of elements is to use the Mohs scale, which ranks elements on scale between 0 and 10 according to how resistant they are to scratching by other elements.

Another method is to use the Vickers scale, which measures a material's resistance to indentation by a standard source; materials are subjected to an impact by a object of a standard size, shape and mass and then the indentation caused by the impact is measured.

The Hardest Metals

According to the Mohs scale, the 10 hardest metallic elements are, in order of descending hardness, chromium, tungsten, osmium, rhenium, vanadium, iridium, tantalum, ruthenium, uranium and rhodium.

On the Vickers scale, the hardest metallic elements are, in order of descending hardness, tantalum, niobium, titanium, zirconium, lutetium, nickel, vanadium, promethium, iron and gadolinium.

Metal Alloys

The hardness of metallic elements can be modified by combining elements into alloys whose hardness differs from that of the original elements, and the manufacturing process of the alloy can further increase its hardness. For example, hardened steel, which is an alloy of iron and carbon, may have a Mohs hardness rating as high as 8, as compared to iron's Mohs rating of 4, titanium's Mohs rating of 6 and chromium's Mohs rating of 8.5.