Session: 04-04-01: (04-04: Advances in Aerospace Structures and Materials & 04-11: Advances in Mechanics, Multiscale Models and Experimental Techniques for Composites)

Paper Number: 98823

98823 - Selective Laser Brazing, Diamond Grits, Phase-Field Modeling, Wetting Dynamics, Thermal and Residual Stresses 

Diamond tools are widely used as cutting, grinding, drilling, and sawing tools due to their superior hardness, modulus, thermal conductivity, wear-resistance, and chemical inertness. Selective laser brazing of diamond grits to a tool surface, usually a stainless steel substrate, is a promising technology to fabricate single layer diamond tools. In which process, the filler metals are first heated and melted by the laser beam and the following solidification would provide bonding between diamond grits and substrate. Due to the melting, wetting, solidifying and chemical reaction during the brazing process, we could have a much stronger bonding and thus longer tool service life compared to the conventional electroplating process. Two types of filler metals are widely used in the brazing of diamond grits, cooper/silver based low brazing temperature filler metal and nickel based high brazing temperature filler metal, the former has lower brazing temperature thus lower processing requirement but lower strength and wear resistance, and the later has higher strength, wear and corrosive resistance, but suffer from higher possibility of graphitization and higher thermal and residual stresses. Various elements are also added to the filler metals either for reducing the melting temperature or enhance the bonding efficiency of the brazing process, for example tin and titanium for the copper/silver based filler metals and phosphorus, boron, and chromium are added to the nickel based filler metals. Currently, due to the lack of fundamental understanding of complex physical and chemical processes, which including the laser materials interaction, solid-liquid phase transition, fluid dynamics in the melting pool, interfacial wetting dynamics, species diffusion, chemical reaction, the transit evolution of thermal and residual stresses, and the complex coupling of the above mentioned processes, and further due to the difficulties of in-situ observation and measuring of the brazing processes, the design and optimization of the brazing process is still challenging. Here, we present a 3D phase-field modeling to study heating, melting, wetting and the evolution of thermal and residual stresses during the selective laser brazing of the diamond grits. The temperature field distribution, the evolution of interfacial morphology and the transit thermal and residual stresses are computationally resolved with a thermodynamics consistent phase field models. Specifically, heating, phase transition, fluid dynamics, and interfacial wetting dynamics are first simulated with an in house MATLAB based solver based on the phase filed method. The temperature history and the evolving solid field are then imported to ABAQUS to study the evolution of thermal and residual stresses. The model to can enhance our fundamental understanding of the brazing processes and be used to optimize the processing parameters in the brazing process.

Presenting Author: Lu Li Purdue University

Presenting Author Biography: Dr. Li got his Ph.D. from the University of Connecticut in 2021, his research interests are microfluidics, thermofluids, phase-field modeling, spreading and wetting dynamics and crack evolution in composite material.

Authors:

Lu Li Purdue University
Dianyun Zhang Purdue University