The Effect of Substrate Grain Size on Coating Microstructure and Bearing Performance in Multilayer Plating Materials for Engine Bearings

Yuhei Maegawa･Ryuji Kanaya･Yuma Haneda (Daido Metal)

With the aim of improving fatigue resistance for multilayer plating, we examined the control of the substrate microstructure by grain size. The grain size of the substrate can be reduced by changing the amount of metal added, which also affects the grain size of the multilayer plating. The study showed that controlling the grain size of the substrate can change the stress dispersion and crack progress behavior, potentially contributing to improved bearing performance.

Evaluation of Liquid Metal Embrittlement and Spot Weldability in E-Coated, Galvannealed 1.8 GPa Hot-Stamped Steel

Wook Jin Oh･Chang Wook Lee･Dong Ha Kang･Youn Il Jung (Hyundai Motor)･Je Youl Kong･Dong Hyun Kim･Jae Wook Kang (Hyundai Steel)

This study investigates the effects of E-coating on mechanical properties, spot weldability, and liquid metal embrittlement of galvannealed (GA) 1.8 GPa hot-stamped steel. GA steel shows superior elongation and bending performance with Al-10Si coated steel. Liquid metal embrittlement is controlled by heat treatment conditions, requiring adequate holding to suppress zinc penetration. Resistance spot weldability is maintained despite surface oxidation. These results support GA hot-stamped steel application in automotive structural components.

Standard Harmonization in Hydrogen Embrittlement Evaluation Using Equivalent Metrics

Amon Kimura･Satoshi Mizokami･Mitsugi Fukahori (Mazda)

The demand for vehicle weight reduction and improved crash safety has led to the increased application of high-strength steel sheets. For high-strength steels, addressing hydrogen embrittlement is one of the critical reliability issues, and the establishment of appropriate evaluation methods is required. This study reports a method to achieve equivalent hydrogen embrittlement evaluation using four-point bending and U-bend tests employed in domestic and international standards.

Evaluation of Hydrogen Embrittlement Resistance under Dynamic Loading Conditions

Susumu Maeda (Honda R&D)･Junya Suzuki (Honda Motor)･Tatsuya Houda (Honda R&D)･Hideki Tanaka (Honda Motor)･Shuji Ichijo･Mizuki Nihira･Kazuto Goto (Honda R&D)

The mechanism of hydrogen embrittlement under dynamic loading, such as in bearings, has remained unclear, and no definitive conclusion has been reached. In this study, we investigated the effects of additives on oil film formation and the influence of vibration under actual operating conditions to clarify the mechanism and obtained meaningful insights. Furthermore, a practical indicator for evaluating hydrogen embrittlement strength applicable to real operation was established.