This study presents a failure analysis investigation of a stainless steel tube tree sample from an industrial furnace. The study aimed to identify the factors responsible for the failure and explore the underlying mechanisms leading to the observed brittle fracture. Various investigation techniques, including SEM, EDS, stereomicroscope, and mechanical testing, were utilized to perform root cause failure analysis.The findings revealed that the furnace tube support material had undergone sigma phase embrittlement. This phenomenon reduced the material's impact strength, rendering it susceptible to brittle failure under operational conditions. The sigma phase in the microstructure contributed significantly to the observed failure. Understanding these factors is crucial for enhancing industrial equipment design and material selection to prevent similar failures. By identifying sigma phase embrittlement as the primary cause of failure, the study highlights the need to consider material properties and thermal conditions in high-temperature applications carefully.