表面硬度分析對不同氮化層結構的脆性快速評估可行性

本文目的在探討表面硬度測試對合金鋼氮化層的脆性快速評估可行性，利用SKD61、2311及NAK80三種鋼料，經有化合物層氮化、無化合物層氮化以及軟氮化等處理，進行洛氏及維氏硬度試驗，並以掃描式電子顯微鏡觀察表面型態是否剝離，以快速評估表面硬層之脆性破壞狀態。初期結果發現82.5 HRB基地的SKD61氮化試片表面硬化層之雪糕效應明顯。有化合物層之氮化處理調質件在HRC及HRD等高荷重的壓痕，可觀察到較多的擠壓及崩落等現象，但在HR15N等低荷重下，不會觀察到壓痕邊緣之剝落，說明輕荷重無法有評估有化合物層的氮化處理。

This article investigates the feasibility of rapidly assessing the brittleness of nitrided layers on different alloy steels through surface hardness testing. SKD61 steel samples, in both as-received (82.5 HRB) and quenched and tempered (50 ± 2 HRC) conditions, as well as 2311 steel (30 HRC) and NAK80 steel (40 HRC), were subjected to distinct nitriding treatments including nitriding with a compound layer, nitriding without a compound layer, and soft nitriding. Initial findings indicate that the as-received SKD61 steel exhibited a pronounced “ice cream cone” effect in its surface hardened layer, characterized by more significant spalling and cracking compared to the quenched and tempered material under identical hardness testing conditions. For quenched and tempered samples subjected to nitriding with a compound layer, high-load indentations (e.g., HRC and HRD) revealed considerable extrusion and collapse phenomena, which can be directly correlated with increased brittleness, whereas under low-load conditions (e.g., HR15N), intact indentation edges and higher hardness values were observed without spallation around the indentation perimeter, suggesting that light-load hardness tests are ineffective for evaluating the brittleness of compound-layer nitrided surfaces.