Metal-reinforced diamond composite films produced by a three-step process are studied by examining the nature and interaction of the three types of interfaces present in the composite: diamond-substrate, binder-substrate and diamond-binder. Diamond composites were deposited on tungsten substrates with nickel or CuTiAg alloy binders. It is found that a diffusion bond formed between the binder and the substrate. In addition, carbide-forming elements are found to segregate to the diamond-binder interface. The binding state of the diffused elements was studied by examining the fine structure of the Auger spectra. Carbon at the interface between the binder and the diamond is found to have carbide-type bonding which should improve the adherence of the binder to the diamond.