EFFECT OF HEAT-TREATMENT ON PHASE RELATIONSHIPS, MICROSTRUCTURES AND HARDNESS OF Co-Cr-Mo ALLOYS

MEHMET YILDIRIM; ALİ KELEŞ

EFFECT OF HEAT-TREATMENT ON PHASE RELATIONSHIPS, MICROSTRUCTURES AND HARDNESS OF Co-Cr-Mo ALLOYS

MEHMET YILDIRIM, ALİ KELEŞ

Öz

The effect of heat-treatment on phase relationships, microstructures and hardness of Co-Cr-Mo alloys were investigated in detail. The samples were produced by investment casting technique and subsequently solutionized (1240 °C for 4 h) and aged (720 °C for 2, 4, 8 and 16 h). Phase analysis of the samples were performed via X-ray diffraction analysis, microstructural examination were done by light optical and scanning electron microscopy. The microstructures of as-cast and short-time (2 and 4 h) aged samples were composed of FCC γ-Co matrix phase and fine M₂₃C₆ (where M= Co, Cr and Mo) precipitates. Increasing the aging time to 8 and 16 h led to partial transformation of FCC γ-Co matrix phase into HCP ε-Co phase. The volume fraction of ε-Co phase increased with increasing aging time. Moreover, hardness of the Co-Cr-Mo samples were significantly enhanced with formation of ε-Co phase.

Anahtar Kelimeler

Co-Cr-Mo alloys, Microstructure, Hardness

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