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

Abstract

The tempering response of CPM® 3V tool steel was investigated via a hardening and tempering heat treatment, tensile testing, fractography, and microstructural evaluation. CPM® 3V tool steel is manufactured using Crucible Particle Metallurgy (CPM®), 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 °C, 550 °C, 650 °C, and 700 °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 °C were dominated by brittle failure while samples tempered at >550 °C experienced ductile failure. The 550 °C treatment showed mixed ductile and brittle fracture features. This study found that CPM® 3V can be optimized for strength, with good tensile toughness, at a 550 °C tempering temperature. This is consistent with Crucible Industries’ recommended tempering temperature for good wear resistance and toughness.