Influence of Ductility on Fracture in Tensile Testing of Cold Gas Sprayed Deposits

Abstract

AbstractCold gas spraying nowadays receives much interest for additive manufacturing due to its high deposition rate. Associated structural applications define high requirements regarding mechanical properties and failure tolerances. Up to present, micro-flat tensile (MFT) or tubular coating tensile (TCT) tests are well-established for determining deposit strengths. Due to particular stress states during testing, both provide slightly different information. While MFT tests can provide information on strain and ductility, stress concentration in TCT tests requires to apply a notch factor for calculating the ultimate tensile strength. Here, we suggest that a suitable combination of both tests can provide additional information about tolerances against local stress concentrations in crack initiation and growth. Taking titanium and copper as model systems, results from MFT and TCT tests are evaluated over a wide range of spray parameter sets into regimes that allow for high deposit qualities, even reaching certain ductility. The correlation between the results reveals that the derived stress concentration sensitivity depends on the deposit quality and could eventually decrease to unity. In turn, the correlation to respective strain to failure data can supply information on underlying deformation mechanisms. These preliminary results thus provide strategies for tuning deposit toughness and give prerequisites for quality forecasts.