Influence of cold sprayed Cr3C2-Ni coating on fracture characteristics of additively manufactured 15Cr-5Ni stainless steel

Highlights: • Grain size reduction in 15-5 PH stainless steel substrate is observed after cold spray deposition of a Cr₃C₂-Ni coating. • A cold spray deposited Cr₃C₂-Ni coating has a beneficial influence on nanohardness of 15-5 PH stainless steel substrate. • Improved nanomechanical and fine grain structure at and ahead of the crack tip is correlated to the Cr₃C₂-Ni deposition. • An improvement in fracture toughness (K_IC) and fatigue performance of cold sprayed 15-5 PH stainless steel is observed. In this research the influence of heat treatment and a combination of heat treatment and a cold spray (CS) coating on tensile, fracture toughness, and fatigue characteristics of additively manufactured 15-5 precipitation hardenable stainless steel (15-5 PH SS) was studied. Test specimens of ASTM standard geometry were produced by direct metal laser sintering of 15-5 PH SS powder and subsequently heat treated. A thin layer of chrome-carbide nickel (Cr₃C₂-Ni) was deposited on the specimens using CS, which were then subjected to ASTM tensile, fracture toughness, and fatigue crack growth rate tests. In addition, to examine the influence of CS coating on the microscale properties and fracture morphology of heat treated 15-5 PH SS a series of test including, microstructure analysis, nanoindentation, and fractography were performed. CS deposition of Cr₃C₂-Ni on the additively manufactured 15-5 PH SS was found to have a beneficial influence on the uniaxial tensile strength and fracture toughness. Also, fatigue crack growth rate results indicated a notable enhancement in the near threshold, Paris, and fracture toughness. Improvements in the fracture characteristics were associated with the significant contribution of CS coating on grain size refinement and improvement of nanomechanical properties at and ahead of the crack tip.