Advanced Martensitic Stainless Steels for Dental Instruments

The developed microstructures and tensile strength of AISI 420-type martensitic stainless steels with different carbon content from 0.2 to 0.4% were studied after tempering at 450°C for 3 h and at 800°C for 16 h. The volume fraction of retained austenite depends significantly on the carbon content. The fraction of retained austenite is about 0.3 after tempering at 450°C for 3 h in steels with 0.3–0.4% carbon. An average grain size comprises 0.97 μm and 0.6 μm after tempering at 450°C for 3 h in the steels with carbon content of 0.2 and 0.4%, respectively. Tempering at 800°C for 16 h increases the grain size to 2.1 μm in the 0.2% C steel and to 1.3 μm in the 0.4% C steel. The phase transformation during high temperature tempering is accompanied by recovery and subgrain coalescence. Depending on the carbon content, a tensile strength of 1700–1900 MPa or 650–750 MPa can be achieved after tempering at 450°C or 800°C, respectively.