超音波ナノ結晶表面改質および電解プラズマ表面改質技術によるAISI 52100鋼の表面硬化と耐摩耗性に関する研究

A Study on Surface Hardening and Wear Resistance of AISI 52100 Steel by Ultrasonic Nanocrystal Surface Modification and Electrolytic Plasma Surface Modification Technologies.

抄録

本研究では、AISI52100軸受鋼の表面硬化を超音波ナノ結晶表面改質（UNSM）および電解プラズマ熱環表面改質（EPSM）により行い、耐摩耗性に及ぼす影響について検討した。これらの処理が耐摩耗性に及ぼす影響を評価するため、ASTM G99に準拠したボールオンディスク型トライボメータを用いて、乾燥条件下での摩擦試験を実施した。処理前後の試料の微細構造を走査型電子顕微鏡で観察した。また、ビッカース硬度計を用いて、上面からの深さに対する微小硬度を測定した。組織観察の結果、EPSM処理では表面層に残留オーステナイトが形成され、UNSM処理では試料表面に表面強塑性変形層が形成された。処理層の微小硬度の増加は、室温でのUNSM処理後と、異なるサイクルでのEPSM処理後に確認された。耐摩耗性が最も向上したのは，700 ℃でUNSM処理を行い，EPSM処理を5サイクル行った試料であった．さらに，摩擦係数や硬さと相関のある摩耗量を測定した．

In this study, a surface hardening of AISI 52100 bearing steel was performed by ultrasonic nanocrystal surface modification (UNSM), and electrolytic-plasma thermo-cyclic surface modification (EPSM), and their effects on the wear resistance were investigated. To evaluate the impact of these treatments on the wear resistance, the friction tests under dry conditions were conducted using a ball-on-disk tribometer in accordance with ASTM G99. The microstructure of the samples before and after treatment was characterized by scanning electron microscopy. The micro-hardness with respect to the depth from the top surface was measured using a Vickers micro-hardness tester. Microstructural observations showed that EPSM treatment led to the formation of residual austenite in the surface layer, while UNSM treatment led to the formation of a surface severe plastic deformation layer on the surface of the samples. The increase in the micro-hardness of the treated layer was confirmed after UNSM at room temperature and after EPSM at different cycles. The highest increase in wear resistance was observed for the specimen treated by UNSM treatment at 700 °C and five cycles of EPSM treatment. In addition, the wear volume, which has correlation with the friction coefficient and hardness, was determined.