Fracture toughness and fatigue crack growth in DMLS Co-Cr-Mo alloy: Unraveling the role of scanning strategies

Co-Cr-Mo alloy is crucial for biomedical implants and aerospace components. These parts often exhibit a high level of geometric intricacy. Direct metal laser sintering (DMLS) is ideal for these complex parts. In DMLS, choosing the right scanning strategies is vital, as it significantly affects the fatigue fracture behavior of the printed components. Thus, the present study investigates the effect of different scanning strategies (stripe, meander, and chessboard) on the fracture toughness and fatigue crack growth behavior of DMLS printed Co-CrMo alloy. For each scanning strategy, fatigue crack growth tests have been performed to evaluate the threshold stress intensity factor and Paris law constants. To corroborate the obtained experimental results, microstructure analyses have been performed using electron backscattered diffraction. Further, failure mechanisms have been identified from fractographs obtained using field emission scanning electron microscopy. It is evident from the obtained test results that scanning strategies caused significant variation in fracture toughness and fatigue crack growth behavior. The stripe scanning strategy has exhibited higher resistance to fracture and fatigue crack growth. However, delayed crack initiation has been observed in the case of the chessboard scanning strategy. The present study provide the background for better selection of scanning strategies to mitigate fatigue fracture in DMLS-printed Co-Cr-Mo alloy designed for specific applications.