Mechanical and Microstructural Behavior of Tempered CPM® 3V High-Density Sintered Tool Steel

The tempering response of CPM (R) 3V tool steel was investigated via a hardening and tempering heat treatment, tensile testing, fractography, and microstructural evaluation. CPM (R) 3V tool steel is manufactured using Crucible Particle Metallurgy (CPM (R)), a proprietary high-density sintering technique developed by Crucible Industries. The hardening and tempering heat treatments were applied to ASTM E8 standard test specimens. Tempering temperature was the experimental variable. The following samples were prepared: As-Hardened (no tempering); tempered at 450 degrees C, 550 degrees C, 650 degrees C, and 700 degrees C; and As-Received (annealed). Ultimate tensile strength and the yield strength of each treatment was determined using the ASTM E8 standard tensile test. The failed specimens were examined for mode of fracture at macro- and microscopic scales. Reflected light microscopy and a scanning electron microscope (SEM) was used for microstructural characterization. Testing and analysis established the samples tempered at <550 degrees C were dominated by brittle failure while samples tempered at >550 degrees C experienced ductile failure. The 550 degrees C treatment showed mixed ductile and brittle fracture features. This study found that CPM (R) 3V can be optimized for strength, with good tensile toughness, at a 550 degrees C tempering temperature. This is consistent with Crucible Industries' recommended tempering temperature for good wear resistance and toughness.

Automated summary

By investigating the tempering response of CPM (R) 3V tool steel, an optimal tempering temperature of 550 degrees C was identified to achieve improved strength while maintaining good tensile toughness.