Word Enhancement of Tongue Depressor Hardness by Heat Treatment and Shot Peening

Abstract

Tongue depressor is a tool commonly used in the medical world in health examinations especially in the mouth area. Tongue depressors generally is made by wood that is considered biodegradable. Currently, metal material has been used as a material tongue depressor like stainless steel because it is considered more easily sterilized so it can be used repeatedly. The main content of human saliva is acid which tend to corrode metal. For that, the use of stainless steel as a tongue depressor has a deficiency that is easily corroded. Therefore, other metal materials such as AISI 316L Stainless Steel which are stainless steel with low carbon content (0.03% C) are required and have high corrosive resistance. With low carbon content AISI 316L Stainless Steel is suitable for surgery tools and diagnostic tools. The reduction of metal corrosion rate can also be done by the shot peening process by hitting the surface of the material by using a steel ball medium (stainless steel ball). The balls are fired using a gun blaster with high pressure so that the material surface collides with the steel balls that cause a strong impact on the surface of the material. Due to the strong impact resistant material surface, the AISI 316L Stainless Steel grain structure will be softer that the material has better mechanical properties. Shot peening increase the material hardness, therefore heat treatment is required to reduce the hardness so that AISI 316L Stainless Steel material can be used as tongue depressor which need strong but flexible. AISI 316L Stainless Steel with dimensions 30 mm long, 30 mm wide and 2 mm thick is used as a test material. The stainless steel ball used in this study is 5 mm in diameter. The process of shot peening is done using a compressor and gun blaster. After the shot peening, the specimens are heated in an electric furnace with temperature variations of 750°C, 800°C, and 850°C and holding time for 2 hours then cooling process is full annealing and normalizing. Furthermore, a hardness test was conducted. In the heat shooting process the heat treatment and cooling method selection also influence the level of hardness, for heat treatment. Annealing temperature 750°C with cooling method in furnace, the hardness of material increased to 177.68 VHN, while in other heat treatment experience increase of hardness.