Material characteristics

Various degradation rates of materials are accelerated in high-temperature environments, and the organization is prone to instability, deformation and crack growth under the action of temperature and stress, and oxidation and corrosion of the material surface during use.

1. High temperature and corrosion resistance

The high temperature resistance and corrosion resistance of superalloys mainly depend on its chemical composition and organizational structure. Taking GH4169 nickel-based deformed superalloy as an example, it can be seen that the niobium content in GH4169 alloy is high, and the degree of niobium segregation in the alloy is directly related to the metallurgical process. The matrix of GH4169 is Ni-Gr solid solution, and the content of Ni is more than 50%. The high temperature is about 1 000℃, similar to the American brand Inconel718. The alloy is composed of γ matrix phase, δ phase, carbide and strengthening phase γ'and γ″ phase. The chemical elements and matrix structure of GH4169 alloy show its strong mechanical properties. Yield strength and tensile strength are several times better than 45 steel, and plasticity is better than 45 steel. The stable lattice structure and a large number of strengthening factors construct its excellent mechanical properties.

Ni Cr Mo Ti Nb A l Fe

51. 96 17. 98 3. 07 0. 95 4. 82 0. Over 45

Table 1 The main chemical components of GH4169 (mass fraction %)

2. High-temperature alloy with high machining difficulty Due to its complex and harsh working environment, its machined surface integrity plays a very important role in its performance. However, superalloy is a typical difficult-to-machine material, which has high micro-hardness and severe work hardening, high shear stress and low thermal conductivity, and high cutting force and cutting temperature in the cutting area. In the process of machining, problems such as low surface quality and very serious tool damage often occur. Under general cutting conditions, the surface layer of superalloys will have too large problems such as hardening layer, residual stress, white layer, black layer and grain deformation layer.