Methodology for Studying Effect of Cooling Rate During Laser Deposition on Microstructure

The present paper focuses on the effect of cooling rate and other processing variables on microstructure and mechanical properties. A specially designed, namely "step shape," was used in the current study. The influences of the step thickness were investigated. Results show that the cooling rate is different at different steps and changes the solidification of the deposition process. The cooling rate was deliberately controlled by employing the substrate of varied dimensions. Thermocouples were used to measure the local temperature of the substrate during the deposition process and cooling stage until it reached room temperature. The results of the temperature-time relationship proved the difference in cooling rate. The influence of the substrate dimension on the microstructure and mechanical properties was investigated. The differed cooling rate led to varied grain size and resulted in affected varied hardness and tensile strength. The small samples possessed larger grains sizes formed by a slower cooling rate. The results open the possibility to acquire continuous varied microstructure and mechanical properties by employing a "step shape" substrate.