High Temperature Materials

High Temperature Materials are materials which withstand higher temperatures.This presentation gives basic information regarding them.

1. Prepared by: Shruti Bhagwatrao Chaudhari HIGH TEMPERATURE MATERIALS

2. Introduction Mechanical Properties of regular engineering materials are affected by change in Temperature. Special High Temperature materials are used for high temperature working conditions.

3. Effect of Temperature on Mechanical Properties

4. Properties of High temperature Materials High temperature resistance High oxidation and corrosion resistance High creep and fatigue strength Resistance to grain boundary Resistance to grain boundary weakening

5. Types of high temperature materials

6. Iron Base Alloys Regular iron and carbon steels have poor tempering and creep resistance upto 450⁰C Plain Carbon steel is alloyed with Mo, W, Va and Cr to improve creep resistance. Iron base Carbon steels: 1)Low alloy steel 2)Medium alloy steel 3) High alloy steel

7. Iron base casting alloys: 1)Iron Chromium alloy 2)Iron Chromium Nickel Alloy Wrought Iron base alloys: Varying alloy elements composition

8. Nickel base alloys Nickel has very low coefficient of thermal expansion. Nickel is alloyed with Cr, Mo, and Co to improve specific properties. Different Nickel base alloys are: 1) Ni-Cr H igh resistance to corrosion High thermal shock resistance

9. 2)Ni-Cr-Mo High resistance to corrosion High strength 3)Ni-Cr-Co High strength 4)Ni-Cr-Co-Mo High temperature strength and corrosion resistance.

10. Cobalt base alloys Very high red hardness High corrosion and wear resistance Expensive Cobalt is alloyed with CR, Ni, W & Mo They are used in cutting tool making, turbine blades, jet engines and afterburners.

11. Refractory metals and alloys They can withstand very high temperatures. High wear and corrosion resistance Very low coefficient of thermal expansion Due to cost and availability reasons, alloying elements are used selectively and in smaller proportions Refractory ceramics are used in furnaces, crucibles, molten metal carrying vessels.

12. Refractory materials can be grouped as: a ) Acid Refractories - made of silica, aluminium silica, alumina,etc b) Basic Refractories - made of magnesia, bauxite,dolomite,etc c) Neutral Refractories : made of chromite , graphite,etc

13. Important Refractory Materials & Applications Material Composition Working Temp. Applications Graphite Carbon 3000 Heating Rods Thoria ThO 2 2750 Jet Nozzles Magnesia MgO 2000 Basic steel making Alumina Al 2 O 3 1860 Thermocouple Quartz SiO 2 1700 Alloy steel making Fireclay 40-60% Al 2 O 3 60-40% SiO 2 1300 Furnace lining

14. Ceramics and metal ceramics Ceramic is a compound formed by combination of inorganic and non metallic materials. It is derived from Greek word Keramos meaning burnt potter’s clay or earth. Ceramics are hard and brittle materials.

15. They have high abrasion resistance, heat resistance and can withstand high compressive stresses. Ceramics are mostly crystalline in structure but due to different chemical compositions their structure becomes more complex. Non metal ceramics have poor thermal and mechanical shock absorbing resistance.