The Formation of NiCrAlY Laser Cladding with Preplaced Method

Abstract

Cladding techniques have been used in many areas. Recently laser cladding techniques have been developed and applied to the automobile parts fabrication and to the repair of pipes inside installed in the Nuclear Power Plants.
As for the laser cladding, there are the following three methods of supplying the cladding material ; (1) Wire feed, (2) Powder feed and (3) Preplaced powder. The third method was selected for having higher flexibility in selecting the chemical composition of cladding material and cladding position. The investigation was carried out to produce a NiCrAlY cladding layer.
Cladding parameters such as laser power, traveling speed, diameter of powder and cladding atmosphere were changed systematically to select the best condition for a single bead with a low power (1200 W) CO₂ laser. A SUS304 plate with a 12 mm thickness was used as a substrate, and mixed powders were bedded with a 1 mm thickness with an organic binder. The dilution ratio and the cross sectional area of the cladded layer were measured and the best cladding conditions were selected on the basis of these data.
To get a large cladded area a weaving method and a half lapping method were tried based on the best cladding conditions for the single bead.
The results obtained are as follows ;
1. The NiCrAIY laser cladded layer with good characteristic can be obtained by mixing commercial powders of Ni-Cr, Al and Y-Ni and a commercial organic binder.
2. With the weaving method, a broad area can be cladded with a low power (1200w) CO₂ laser.
3. The uniform distribution of chemical composition throughout the cladded layer thickness can be obtained.
4. An atmospheric chamber replaced inside with Ar can make the layer's contour better.
5. Fine powder was preferred from the points of view of the dilution ratio and the cross sectional area of cladded layer.
6. Carbon content of the cladded layer was not so high although the organic binder was used as the binder, and this shows the high possibility of this method to prepare corrosion resistant cladded layer.