Atsushi Hasui

A study of the bonding mechanism of sprayed coatings

The adhesive mechanism of plasma jet-sprayed nickel, chromium, molybdenum, tantalum, and tungsten coatings on aluminum and mild steel substrates was investigated. The compositions of the boundary layers between the coatings and the substrates were studied using x-ray diffraction. Experiments on the bonding behavior between substrates and nickel drops heated by the levitation melting process were also performed. The results of the experiments show that: (i) the substrate surface is melted by the sprayed particles, and a boundary layer which consists of an intermetallic compound consisting of the elements of the coating and substrate materials is formed between the coating and the substrate; (ii) this layer is necessary to improve the adhesion between the sprayed coating and the substrate; (iii) the adhesive mechanism between the sprayed coating and the substrate surface and the composition of the boundary layer were confirmed by a liquid nickel-drop experiment.

Study on Press-sintering of Sprayed Coating

The press-sintering process of the sprayed coating to improve the denseness and the bonding of the deposited coating has been developed. This new process is superior to the conventional fusing process in which the structural change and the thermal strain of the substrate take place during the treatment. Then, the press-sintering process is applied to a Nickel base self-fluxing alloy coating deposited by oxy-acetylene flame spraying process. Some properties of the press-sintered coating are also investigated.In conclusion, it is clear that the coating, sintered under suitable pressing, has almost the same denseness and bonding as the fused coating, and a higher wear resistance than the fused one.

Some Experiments with a New-Designed Fricition Welding Machine

The friction welding process is developed so as to remove the flash, which protrudes from the contact area between works, by the tool as soon as it is generated. In friction welding of plain carbon steel to plain carbon steel, stainless steel to stainless steel, plain carbon steel to stainless steel and chromium-molybdenum steel to stainless steel, the joint, which has been finished at the moment welding is formed, can be gotten. Moreover, the joint with 100 per cent joint efficiency can be formed by a considerably low welding pressure such as 2, 3 or 4 kg/mm2.