DIFFUSION BONDING OF STEEL TO TI-6AL-4V TO PRODUCE HARD WEARING SURFACE-LAYERS

Titanium is a light, strong alloy used extensively in applications whe re weight saving is important. However, the surface does not resist ab rasion with the result that it cannot be used in applications where th e component must resist wear, such as gear components. Attempts to har den the surface, such as nitriding, have met with limited success. To produce a light component with a hard wearing surface, steel has been diffusion bended to titanium. This has been done using a bench top dif fusion bonding rig, operating in vacuum at temperatures up to 1273 K, which has been designed and built in house. Computer control allows pr edetermined stresses and strains to be carefully controlled. The diffu sion bond has been achieved both without interlayers and with up to th ree interlayers of elements such as copper, vanadium and nickel. The d iffusion bonding of both flat and grooved surfaces has been investigat ed. Results are presented showing the effect of stress, strain, surfac e finish and interlayers on the strength of the diffusion bond. In man y cases bond strengths approaching that of the bulk matrix have been a chieved. The microstructure of the interfaces have been characterized using optical metallography and scanning electron microscopy. (C) 1998 American Vacuum Society.