This content is not included in your SAE MOBILUS subscription, or you are not logged in.
Laser Cladding With Composite Powders Using Pyrometric Temperature Control and Beam Combining
Published September 13, 1993 by ISATA - Dusseldorf Trade Fair in United Kingdom
Event: ISATA 1993
The main purposes of laser surface treatment are to enhance the resistance of metal surfaces against friction, abrasive and erosive wear, corrosion and high temperature oxidation. The highest abrasive wear resistance is shown by composite materials containing high amounts of hard particles embedded in a ductile metallic matrix. Such ceramic/metal composite layers can be produced by laser cladding with heterogeneous powder mixtures of carbide particles and metallic binders. The three major problems of the laser cladding process with such composite powders are the dissolution of the carbide particles, the formation of cracks and the dilution with the substrate material. All these problems are mainly due to the uncontrolled surface temperature within the cladding process.
In this paper three different ways of temperature control to avoid the mentioned processing faults are described. High carbide contents, that means low degrees of carbide dissolution, can be achieved regulating the melt pool temperature at a low level. This can be realized by a fast pyrometric temperature control system. A decrease of the crack formation can be obtained using a second laser beam for simultaneous pre- or post-heating leading to a reduction of the thermal stresses during the cladding process. The second laser beam can also be applied to keep the surface temperature of the substrate constant. A constant surface temperature together with an optimized output power of the processing beam can be used to minimize the dilution of the cladding layer with the substrate material.
Experimental results with two different kinds of powder mixtures (NiCrBSi/WC and NiCrBSi/TiC) show that the pyrometric temperature control in combination with the beam combining method is a useful instrument to enhance the quality of laser-cladded composite layers.