Failure mechanism of sputtered Ta coatings on short rifled gun bore under vented vessel tests

Tantalum is a promising candidate for chromium electrodeposition in large gun bore coatings. However, brittle β-Ta phase can be easily obtained by magnetron sputtering at low temperatures. In this study, Ta coatings were deposited on the inner surfaces of short rifled tubes using high-power impulse magnetron sputtering technology. The Ta coatings were confirmed to be pure α-Ta phase. When subjected to vented vessel test (VVT) firings, all α-Ta coatings exhibited excellent adhesion. After 10 VVT firings, the total average mass loss was only 0.07 g, indicating strong anti-ablation property against 320 MPa gunpowder explosions. A chemically affected zone eroded by the gunpowder explosion was formed less than 2.1 μm. Additionally, several bulges form on Ta coating surface. This primary failure mode is attributed to decarbonization behavior during VVT firings, while the external collapse of interfacial carbon leads to the formation of bulges and opening cracks in the coating.