Microwave hybrid heating (MHH) of Ni-based alloy powder on Ni and steel-based metals –A review on fundamentals and parameters

Abstract

Microwave hybrid heating (MHH) is widely used for rapid heating and short-time reaction in the food industry and scientific fields. MHH processes also include the implementation of lightweight metals joints such as Ni-based alloys. The advantages of using the MHH technique are providing sufficient joint between similar or dissimilar lightweight metals, which reduces the time needed to melt and reduces defects on the joint surface. However, for the MHH applications, major parameter settings and design models of heating have not been extensively explored. Ni-based alloy powder (approximately 9–10%) exhibits low ductility because of its poor solidifying property and high melting point at room temperature. This phenomenon has caused some challenges for weldability in various manufacturing processes. In order to attain the melting point in a shorter time, researchers had implemented microwave hybrid heating (MHH) techniques by improving the rapid heating rate, mechanical characteristics (tensile strength and hardness), and microstructures properties by using carbon-based (absorber) and silicon-based materials (insulator). This paper aims to review the joint of Ni-based alloys on steel-based materials by using the MHH approach. In this review, the main structures of application (cavity design), design of heat application (heat materials), and various crucial parameters settings were discussed. It can be noticed that charcoal and graphite powder were frequently used in the MHH system due to its better effectiveness. Most of the literatures used the microwave frequency between 2.00 – 2.45 GHz, whereby the microwave power was set between 800 – 900-Watts with exposure time between 300 to 720 s to observe high penetration depth for the joining of Ni-based alloy powder.