Refractory fracture mechanics

Stacking faults thereby providing barriers to sHp. If carbides are allowed to precipitate to the point of becoming continuous along the grain boundaries, they often initiate fracture (see Fracture mechanics). A thorough discussion of the mechanical properties of cobalt alloys is given in References 29 and 30 (see also Refractories). 

The requirements for an FSW tool in high-temperature materials (HTM) are significant. Obviously, the tool must maintain sufficient strength to constrain the weld material at softening temperatures in excess of 1000 °C (1830 °F). Perhaps less apparent, the tool must also be resistant to fatigue, fracture, mechanical wear, and chemical reactions with both the atmosphere and the weld material. To date, two classes of materials have been found that meet these requirements refractory metal tools and superabrasive tools. 

Table 3.1-115 Fracture mechanical data for various refractory metals, pretreatment Aw = as worked, Sr = stress relieved, Rxx = recrystallized. RT = room temperature...

Harmuth H, Bradt RC. Investigation of refractories brittleness by fracture mechanical and Fractographic methods. Interceram Ref Refractories Man. 2010. 

The first three chapters provide the fundamentals of refractories. Refractories deteriorate from either or both chemical and mechanical effects. The fundamentals of refractory material properties are addressed in Chapter 1. Fracture mechanics or those aspects of the mechanical deterioration of refractories are provided in Chapter 2. Chapter 3, on the corrosion of refractory brick, looks at the chemical deterioration of refractories. 

SAK 86] SAKAI M. and BRADT R.C., Graphical methods for determining the non-linear fracture parameters of silica and graphite refractory composites , in Fracture mechanics of ceramics, vol. 7, Ed. Bradt R.C., Evans A.G., Hasselman D.P.H. and Lange F.F., Plenum Press, New York, 1986. 

The other mechanical properties - especially fracture strength and fracture toughness - are usually inferior to those in other structural oxide ceramics such as zirconia. The presence of glass decreases the Young s modulus, and also the strength, hardness, and refractoriness of alumina ceramics. The typical properties of aluminas of various purities are listed in Table 1.2 [50]. 

---