PSI - Issue 75

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ScienceDirect Available online at www.sciencedirect.com ^ĐŝĞŶĐĞ ŝƌĞĐƚ Structural Integrity Procedia (2025) 000 – 000 Available online at www.sciencedirect.com ^ĐŝĞŶĐĞ ŝƌĞĐƚ Structural Integrity Procedia (2025) 000 – 000 Available online at www.sciencedirect.com Procedia Structural Integrity 75 (2025) 442–449

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Fatigue Design 2025 (FatDes 2025)

© 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of Dr Fabien Lefebvre with at least 2 reviewers per paper The investigation consisted in a deep analysis of the microstructure of both valves especially in the stem and in the head. It is shown that the evolution of the microhardness along the valve from the stem top to the head bottom was constant in the unused valve but exhibited a marked drop in the head area of the used valve. SEM-EBSD analysis point out grain coarsening and carbide growth in the valve fillet. Comparison with the microstructure of the stem which is essentially only thermally loaded allowed concluding that the modification of the microstructure resulted from cyclic loading at high temperature. Additional fatigue indicators were also found by TEM analysis which revealed the presence of twist boundaries typical of high temperature fatigue Keywords: forensic metallurgy; historical metallurgy; silchrome 1; X45CrSi9-3; EN 52 steel; silchrome; poppet valve; heat resistant steel; combustion engine; heat treatment The investigation consisted in a deep analysis of the microstructure of both valves especially in the stem and in the head. It is shown that the evolution of the microhardness along the valve from the stem top to the head bottom was constant in the unused valve but exhibited a marked drop in the head area of the used valve. SEM-EBSD analysis point out grain coarsening and carbide growth in the valve fillet. Comparison with the microstructure of the stem which is essentially only thermally loaded allowed concluding that the modification of the microstructure resulted from cyclic loading at high temperature. Additional fatigue indicators were also found by TEM analysis which revealed the presence of twist boundaries typical of high temperature fatigue Keywords: forensic metallurgy; historical metallurgy; silchrome 1; X45CrSi9-3; EN 52 steel; silchrome; poppet valve; heat resistant steel; combustion engine; heat treatment Microstructure degradation in the Silchrome 1 steel by high temperature VHCF: a case study Jérémie BOUQUEREL a *, Jan RUZICKA a,b , Jean-Bernard VOGT a a. Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, F-59000 Lille, France b. University of Chemstry and Technology, Prague, Czech Rep. Abstract The different components of internal combustion engines, especially valves, operate in complex conditions. High temperature, cyclic thermal and mechanical loading, and corrosive medium are interactive damage sources. This requires optimizing the choice of material to satisfy their long-durability and high reliability to avoid valve failures. Silchrome 1, a martensitic steel with the chemical composition - C 0.40 – 0.50, Cr 8.00 – 10.00, Si 2.70 – 3.30, Mn 0.50 – 1.50, P max 0.040, S max 0.030, Ni max 0.50 wt% - appeared to be suitable for valve fabrication because it maintains its properties up to 600 – 650 °C under a high dynamic load. Even though Silchrome 1 has been designed and used since the 1920s and it is still in use today. The present paper focuses on an investigation of two exhaust valves fabricated in 1942 for a Harley-Davidson WLA/WLC motorcycle. The first one is unused and comes from a surplus replacement kit. The second one has been extracted from a motor which motorcycle has driven for 300 000 km. Microstructure degradation in the Silchrome 1 steel by high temperature VHCF: a case study Jérémie BOUQUEREL a *, Jan RUZICKA a,b , Jean-Bernard VOGT a a. Univ. Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, F-59000 Lille, France b. University of Chemstry and Technology, Prague, Czech Rep. Abstract The different components of internal combustion engines, especially valves, operate in complex conditions. High temperature, cyclic thermal and mechanical loading, and corrosive medium are interactive damage sources. This requires optimizing the choice of material to satisfy their long-durability and high reliability to avoid valve failures. Silchrome 1, a martensitic steel with the chemical composition - C 0.40 – 0.50, Cr 8.00 – 10.00, Si 2.70 – 3.30, Mn 0.50 – 1.50, P max 0.040, S max 0.030, Ni max 0.50 wt% - appeared to be suitable for valve fabrication because it maintains its properties up to 600 – 650 °C under a high dynamic load. Even though Silchrome 1 has been designed and used since the 1920s and it is still in use today. The present paper focuses on an investigation of two exhaust valves fabricated in 1942 for a Harley-Davidson WLA/WLC motorcycle. The first one is unused and comes from a surplus replacement kit. The second one has been extracted from a motor which motorcycle has driven for 300 000 km.

* Corresponding author. E-mail address: jeremie.bouquerel@centralelille.fr

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the Fatigue Design 2025 organizers 2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the Fatigue Design 2025 organizers * Corresponding author. E-mail address: jeremie.bouquerel@centralelille.fr

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