Production Engineering Archives | 2026
Authors: Srirod S.; Kongphan P.
DOI: 10.30657/pea.2026.32.4
Journal: Production Engineering Archives
Year: 2026
Publisher: Sciendo
Document Type: Article
Open Access: All Open Access; Gold Open Access; Green Open Access
Cited by: 0
Circulating coins remain indispensable in Thailand despite rapid digitalization, with the 5-baht denomination playing a critical role. Yet, collar dies used in its minting suffer frequent wear and premature failure, increasing production costs. This study systematically evaluated two cold-work tool steels - DIN 2379 (conventional) and Böhler K490 (powder metallurgy) - uncoated and coated with titanium nitride (TiN) or chromium nitride (CrN) via arc-PVD, under industrial high-speed minting. Testing included hardness and scratch adhesion, optical/SEM-EDS wear analysis, regression-based tool life prediction, quantitative coin quality assessment, and economic evaluation. Results demonstrated that substrate-coating synergy was decisive. TiN on DIN 2379 achieved the best overall performance, sustaining ∼1.5 million coins with negligible defects, while uncoated DIN 2379 failed at ∼0.67 million. CrN provided intermediate life (∼0.95 million) but with lower adhesion stability. In contrast, K490 systems terminated early (∼0.8-1.0 million coins) due to Cu-Ni debris accumulation, despite groove wear depths remaining below 4 μm. Regression models predicted >6 million coins for K490, but these values were invalid, highlighting the inadequacy of wear-only criteria. The novelty of this work lies in experimentally confirming, under industrial Thai minting conditions, that debris - not wear depth - governs die termination and product quality. TiN-coated DIN 2379 emerged as the most reliable and cost-effective option (∼175,000 Baht per million coins), providing a framework for die management that integrates wear progression, debris effects, and economic efficiency. © 2026 Sunchai Srirod et al.
Coin minting; Collar dies; Economic evaluation; PVD coatings; Wear mechanisms