This often explains the different performance of one mill over the other during forming, even while meeting the procurement specifications. Because air cooling is relatively uncontrolled, variations in grain size and microstructure can occur. Once ready to be cooled, the ingots or coils are removed from the furnace, and allowed to air-cool. This segregation is why there is a different hardenability at the ends of a coil. Very high temperatures and very long times are used to allow variations in chemistry due to segregation to level out. This annealing process is somewhat specialized, in that the purpose is to level out segregation in steel ingots or continuously cast strip. Homogenization Annealing is an annealing method that is used at the steel mill. Figure 1: Typical homogenization anneal of ingots in a soaking pit at a steel mill. But in all cases, the primary reason for annealing is to soften the part and increase the ductility for forming or machining. There are many different types of annealing that can be performed. Annealing can be performed at the mill, and the material received at the plant ready to be machined, or it can be done in-house to facilitate machining. The purpose of annealing, is to make a part have a uniform microstructure, that is soft, to enable forming or machining.
The resultant microstructures will be predicted using JMatPro (Sente Software, 2018), a software program that allows the prediction of microstructure for many different alloys and ivf Integra (Swerea IVF AB, 2012), which calculates the microstructure based on actual cooling curves of quenchants.
We will use a couple of typical alloys to illustrate the microstructures resulting from different heat treatments. In this column, and in forthcoming installments, we are going to discuss the application of CCT diagrams to actual typical heat treatments. The experimental results showed clearly that TLP joints of these superalloys had different TLP bonding behaviors according to the bonding temperatures, and that microstructures such as dendritic structures and the melting points of the base metals had critical effects on these bonding behaviors.I n the last few installments we discussed the use of Time-Temperature-Transformation and Continuous Cooling Transformation diagrams to understand the phase changes that occur during heat treatment. The microstructural characterization of the joints was examined through optical microscopy (OM) and electron probe micro-analysis (EPMA). TLP bonding was carried out with an amorphous filler metal in various bonding conditions. In this article, TLP bonding characteristics of two types of γ′ precipitation strengthened superalloys − GTD111 solidified directionally and Udimet520 wrought − were investigated to approve this technique for the repair of components.
Transient liquid phase (TLP) bonding is an essential technique for gas turbine component repair. Γ′-Precipitation strengthened Ni based superalloys are extensively being accepted for gas turbine components, because these material have excellent mechanical properties, as well as corrosion and oxidation resistance at high temperatures above 1000 ☌.