Enhanced Surface Protection of In-738LC Ni Based Alloy by Metallic Borides and Aluminium Borate Coating via Short Time Powder Pack Method

In this study, the possibility of powder-pack boriding of the In-738LC superalloy at 900°C for two different short times of 30 and 60 min was explored. Boriding caused to formation of aluminium borate and a superficial metallic boride layer at top surface. It was found that the boride coating was consists of three layers: Al 18 B 4 O 33 and Ti rich boride; Cr rich borides; and W, V and Mo rich borides. Microhardness profile tests confirmed the formation of hard borides on the top of the surface. Weight changes of coated and uncoated samples during heating up to 1000°C revealed that the boriding process had a severe influence on oxidation resistance. This study showed that the complex aluminium borate and metallic borides coatings improved the mechanical properties and refractoriness of In-738LC in which protect the surface against the harsh environment.