Wetting behaviour of nickel-based brazing alloy BNi-5a on conventionally cast and laser-melted austenitic stainless steel 316L

Abstract

Laser beam melting is an additive manufacturing process that enables the production of highly complex components. In this process, metal powder is locally melted using a laser beam and built up layer by layer to form a physical component. Due to the layer-by-layer process manufacturing technique of the additive manufacturing process, the microstructure of a laser-melted 316L austenitic stainless steel differs from that of a conventionally cast material. For brazing technology, the different microstructure morphology is important because it affects the known wetting and diffusion behavior with a brazing filler metal, which affects the ability to produce high-strength brazed joints. Brazeability can be determined by examining the wetting of the brazing filler metal with the material to be joined. Therefore, this study investigates the wetting behavior of nickel-base brazing alloy BNi-5a on conventionally cast and laser-melted 316L austenitic stainless steel. Wetting tests were performed to evaluate the spreading area and wetting angle of BNi-5a on both 316L substrates. The wetting tests were performed in a high-temperature vacuum furnace at 1190 °C for 15 min. The results show that the laser-melted 316L stainless steel exhibits enhanced wettability compared to the conventionally cast material. This is related to a higher surface energy and a more pronounced diffusion mechanism called grain boundary grooving on the surface of the material.

Keywords

• Additive manufacturing
• PBF
• Brazing
• Stainless steel
• Nickel base brazing alloy
• Wetting