Knoop hardness optimal loading in measuring microhardness of maraging steel obtained by selective laser melting. (May 2021)

• Record Type: Journal Article
• Authors: Balos, Sebastian; Rajnovic, Dragan; Sidjanin, Leposava; Kostic, Snezana Ciric; Bogojevic, Nebojsa; Pecanac, Milan; Pavlicevic, Jelena
• Is Part Of: Proceedings of the Institution of Mechanical Engineers. Volume 235:Number 10(2021)
• Page Start: 1872
• Page End: 1877
• Publication Date: 2021-05
• Subjects: Selective laser melting -- Knoop microhardness -- indentation size effect -- load independent hardness; Mechanical engineering -- Periodicals; 621.05
• DOI: 10.1177/0954406219841081
• Languages: English
• ISSNs: 0954-4062

Abstract

Knoop microhardness method possesses several advantages over Vickers testing: lower penetration depth, higher accuracy in indentation measurement, and a better suitability to measuring thin and elongated morphological features. This study explores the optimal loading and load independent hardness of selective laser melted specimens in non-heat-treated and heat-treated conditions, by using different Knoop test loads. The obtained results were used to plot load to indentation size charts, which, in turn, were used to obtain prediction curves in accordance to Meyer, proportional specimen resistance, and modified proportional specimen resistance models. The fitting of fitting curves to the measured values was used to calculate appropriate correlation factors. The results indicate that indentation size effect occurs in all measured specimens. This suggests that there is material true microhardness. Also, the most adequate model was modified proportional specimen resistance, with correlation factors just under one.