Experimentation in revealing the prior austenite grain size of carburized Pyrowear® 53

Pyrowear® 53, UNS K71040, is a premium quality carburizing gear steel with a combination of high-temperature performance, fatigue resistance, deep hardenability, and excellent toughness. The alloy has a resisted softening at elevated service temperatures and possess good temper resistance and high case hot hardness while maintaining high core impact strength and fracture toughness. It is double vacuum processed by vacuum induction melting followed by vacuum arc remelting (VIM-VAR) to provide optimum metallurgical quality.¹ The nominal chemistry in weight % is C 0.11, Si 0.9, Ni 2.0, Mg 0.4, Cr 1.0, Mo 3.25 Cu 2.0, V 0.1, and P 0.005 with the balance Iron.

When Pyrowear® 53 is carburized, it develops a variety of microstructures which are challenging when attempting to reveal the prior austenite grain size. This presentation documents five methods used to reveal or develop and reveal the prior austenite grain size: color etching with Beraha’s #2, hot saturated aqueous picric acid, the McQuaid-Ehn test, oxidation at 1575 °F and 1675 °F. The results of each method are then discussed.

¹ https://www.carpentertechnology.com/alloy-finder/pyrowear-53