Development of a Powder and/or Gas Cementation Process for Coating Molybdenum Alloys for High Temperature Protection

摘要

As prepared W-2 coating on Mo-0.5Ti was found to be essentially MoSi2. Upon exposure at 2700F. the coating becomes three phase and develops an oxidation resistant glaze. A statistically designed experiment was run on two levels of each of nine process variables in order to optimize the W-2 coating process. This experiment indicated that the three most important process variables were time and temperature of processing and mixing of the coating powders. Soundness of the Mo-0.5Ti surface and acid etching of the surface were of secondary importance. Purity, particle size and age of powder mixture and retort material were, statistically, minor in importance. The recommended optimum coating would be produced by processing uncontaminated surface Mo-0.5Ti etched and honed. The work piece should be immersed in a commercial purity, -60 plus 150 mesh powder that is well mixed. The work should be processed twice (12 hours at temperature each time) at 1900F. in a steel retort. The coating produced should have a wear life of 47 hours and a standard deviation of 8 hours at 2700F. under the oxidation conditions used in this program. (Author)