Characterization and Modeling of Microscale Preplaced Powder Cladding Via Fiber Laser

Abstract

Laser cladding (LC) is a material deposition technique, in which a laser beam is used to deposit one or several layers of a certain clad material onto a substrate to improve its wear or corrosion resistance. It can also be used for structural repair. Consequently, it is of interest to characterize the residual stresses and the microstructure along with the clad geometry as a function of process parameters. A 100 W fiber laser and focusing optics capable of producing very small spot sizes (∼10 μm) have been integrated with a micromachining center. This paper focuses on providing a comprehensive metallurgical and mechanical characterization of microscale LC of preplaced powdered mixture of cobalt and titanium on IS 2062 (ASTM A36) substrate. Parametric studies were conducted by varying the scanning velocity, laser power, and spot size to produce clad layers well bonded to the substrate. The results show that the width and height of the cladding increases up to 28% and 36%, respectively, due to the variation in the laser parameters. An increase of up to 85% in the microhardness is observed in the cladded layer with presence of Ti–Co intermetallic compounds at the interface, highlighting the application of the process in improving subsurface properties of existing components. The residual stresses obtained in the cladded layer are compressive in nature, indicating the potential application of this technique for repair of structures. In addition, a finite element model has been developed for predicting the clad geometry using a moving Gaussian heat source. Molten region is determined from the thermal model and Tanner's law has been used to account for spreading of the molten layer to accurately predict the clad geometry. The model predicts clad geometry with reasonable prediction errors less than 10% for most cases with stronger dependence on scan velocities in comparison to laser power.