車用部件表面改質技術開發

Development of surface modification technology for automotive parts

某車用部件採用SCM 415板料，原製程為「衝壓下料→滲碳熱處理→表面鍍鋅」，惟試製樣品於嚴苛耐久性測試中提前發生斷裂，未達性能要求。研究結果顯示，原滲碳熱處理製程參數控制不佳，造成過度滲碳，使熱處理後表面硬度偏高；此外，後續電鍍鋅製程亦存在氫引入之疑慮，可能導致氫脆或延遲破壞。於耐久性測試過程中，表面缺陷因而形成應力集中與缺口效應，成為疲勞裂紋起始源，最終導致部件斷裂。綜合考量部件之強度、耐磨性及耐久性要求，後續將原「滲碳熱處理＋電鍍鋅」製程改採無電鍍鎳表面硬化製程，成功通過耐久性測試。本研究除釐清車用部件失效機制並提出改善方案外，亦以單一表面處理製程取代原有兩道製程，可有效簡化製程、降低生產成本與能源消耗，並兼具製程減量及低碳減排效益。

A certain automotive component is manufactured using SCM 415 sheet material, with the original process consisting of blanking/forming→carburizing heat treatment→zinc plating. However, the test samples fractured prematurely during rigorous durability testing and failed to meet the required performance criteria. The investigation indicated that inadequate carburizing heat-treatment parameters resulted in excessive carburization, leading to excessively high surface hardness after heat treatment. In addition, the subsequent zinc-plating process raised concerns regarding potential hydrogen ingress, which may have caused hydrogen embrittlement or delayed fracture. During durability testing, these effects promoted stress concentration and a notch effect at the surface, serving as initiation sites for fatigue cracks and ultimately resulting in component fracture. Considering the component’s requirements for strength, wear resistance, and durability, the original carburizing heat treatment + zinc plating process was subsequently replaced with an electroless nickel surface-hardening process. The revised process successfully passed the durability testing. This study not only clarified the failure mechanism of the automotive component and established an effective improvement solution, but also demonstrated that replacing two conventional processes with a single surface-treatment process can simplify manufacturing, reduce production costs and energy consumption, and deliver additional benefits in terms of process reduction and low-carbon emissions.