A new method for dating of ancient steel samples using Vickers microhardness

A simple, fast and economic method for age determination of steel samples is presented, based on the change of mechanical properties over time. The mechanical strength was determined by Vickers microhardness testing, finding a linear relationship in between this parameter and the age of the sample. For calibration, four different archaeological samples of different ages were used, all of them hypoeutectoid steels. They were taken from excavation sites spread all over the Iberian Peninsula. The samples’ age ranged from 1st century B.C. up to 18th century A.C. Microhardness was measured on either ferritic or pearlitic zones, obtaining a slightly better regression coefficient for the pearlitic zones, which was attributed to particular characteristics of the samples used. The proposed method should have the potential to be extended to hypereutectoid steels.

[Author's later comment: "This paper was strongly critisized (see letters to the editor Mat. Charact. 54 (2005) 270-275). I now believe that the sample population was indeed too small to prove evidence for a linear relation between hardness and age of steel."]