M. Mańka

The Effect of Heat Treatment on Creep Resistance of Castings from the Modified Superalloy MAR-247

mpact of heat treatment on durability has been evaluated in this study in conditions of high-temperature creep of castings made from nickel superalloy MAR-247 post production rejects. Castings made in the processes of modification and filtration when pouring into moulds were subject to solubilization (1185°C/2 h) with subsequent ageing (870°C/20 h). It has been found on the basis of performed tests that in conditions of high-temperature creep at temperature 980°C with stress σ = 150 MPa the resistance of specimens of coarse-grain structure was significantly higher when compared to fine-grain material. The conditions of initiation and propagation of cracks in these specimens were analysed with consideration of morphological properties of material macro-, micro-and substructure. Moreover, it has been proven that creep resistance of heat treated MAR-247 superalloy significantly improves when compared to its condition after the process of modification only. Macrostructural changes in the MAR-247 superalloy that determine the increase of superalloy creep resistance after solubilization and ageing, as observed in the tests, were also examined.

Analysis of Cracking Process in Conditions of High-Temperature Creep of Castings Form the Modified Superalloy IN-713C

mpact of complex modification and filtration during pouring into moulds on durability has been evaluated in this study in conditions of high-temperature creep of castings made from nickel superalloy IN-713C post production rejects. The conditions of initiation and propagation of cracks in the specimens were analysed with consideration of morphological properties of material macro-, micro-and substructure. It has been demonstrated that in conditions of high-temperature creep at temperature 980°C with stress σ =150 MPa creep resistance of the IN-713C superalloy increases significantly with the increase of macrograin size. Creep resistance of specimens made of coarse grain material was significantly higher than the resistance of fine grain material.