Minimizing Titanium Alpha Case During Vacuum Furnace Heat Treating

The use of titanium as a material for aerospace and medical applications is continually growing.  With additive manufacturing ever accelerating as a production process, the drive to minimize alpha case formation has increased. Even when using good vacuum furnace heat treating practices, alpha case can occur and many process specifications use color as a first post heat treatment acceptance protocol. An investigative study into the use of a color spectrophotometer as a tool to correlate surface color and extent of alpha case in post heat treatment titanium alloys and its results will be discussed.  Best practice methods for furnace conditioning will be presented.  Proper preparation of metallurgical specimens for alpha case determination will be described, with examples of surface conditions and etching effects that can alter the apparent extent of alpha case.