Synergistic enhancement of mechanical and tribological properties in WC-reinforced 316L stainless steel matrix composite fabricated by laser powder bed fusion

Abstract

Austenitic 316L stainless steel, renowned for its excellent toughness and corrosion resistance, is widely used in aerospace, precision molds, and automotive industries. However, its limited strength at both room and high temperatures, coupled with poor tribological properties, restricts broader applications. To address these limitations, this study has fabricated a novel stainless steel matrix composite, 3 %WC/316L, with excellent strength-toughness, heat-resistance, and tribological properties, leveraging the inherent advantages of laser powder bed fusion technology through synergistic strengthening mechanisms: fine grain strengthening, particle reinforcement, and precipitation hardening. Following aging treatment at 800 °C for 2 h, the composite comprises a columnar grain structure with uniformly dispersed partially-melted spherical WC particles (∼1 vol%). A well-bonded diffusion zone with a width of 1∼2 μm forms between the unmelted WC cores and the matrix. Crucially, abundant submicron-scale M₂₃C₆ carbides (100–400 nm) precipitate along grain boundaries and within the columnar grains adjacent to the particles. The composite demonstrates superior mechanical properties: at room temperature, the ultimate tensile strength (UTS), yield strength (YS), elongation to fracture (EL), and impact toughness (α_kv) can reach 802 MPa, 554 MPa, 30.5 %, and 55.5 J/cm², respectively; at 400 °C, UTS, YS, and EL still remain at 616 MPa, 370 MPa, and 20.8 %, respectively. Furthermore, the tribological properties are significantly enhanced: at room-temperature, hardness reaches 18.9 HRC, with the average coefficient of friction (COF) and volumetric wear rate (W_r) reduced to 0.6212 and 50.3 × 10⁻⁶ mm³/(N·m), respectively; at 400 °C, COF and W_r further decrease to 0.5291 and 43.6 × 10⁻⁶ mm³/(N·m), respectively.