Long-Term Hot-Hardness Characteristics of Five Through-Hardened Bearing Steels

摘要

Long-term hot-hardness studies were performed with five vacuum-melted bearing steels tem¬pered to various room-temperature hardnesses: AISI 52100 and the tool steels AISI M-l, AISI M-50, Halmo, and WB-49. Hardness measurements were taken on AISI 52100 at room tempera-ture and at elevated temperatures after soaking it at temperatures to 478 K (400 F) for as long as 1000 hours. Hardness measurements were also taken on the tool steels after soaking them at temperatures to 700 K (800° F) for as long as 1000 hours. None of the tool steel tempered during soaking. AISI 52100 did not temper when soaked at 366 K (200° F) for 1000 hours. AISI 52100 that was initially hardened to Rc 62.5 or Rc 64.5 lost hardness during the first 500 hours of the 1000-hour soak tests at temperatures greater than 394 K (250° F), but it maintained its hardness during the final 500 hours of soaking. Similarly, AISI 52100 that was initially hardened to Rc 60.5 lost hardness during the first 500 hours of the 1000-hour soaking at temperatures greater than 422 K (300° F), but it maintained its hardness during the final 500 hours of soaking.