GH5188 (H188) Cobalt-Based Superalloy Composition Analysis

GH5188 Overview

GH5188 alloy is a solid-solution strengthened cobalt-based superalloy, primarily reinforced by carbides. Compared to nickel-based superalloys, this alloy offers superior creep resistance, thermal corrosion resistance, thermal fatigue resistance, and high-temperature strength. In the 1980s, GH5188 alloy was used in components such as vortex plates and flame guides for the WoZhou-8 aero-engine. Currently, it is selected for manufacturing high-temperature parts like combustion chamber inner walls, outer walls, and sealing strips in certain aero-engines. As a wrought cobalt-based superalloy, GH5188 has a simple microstructure. Due to the stability of carbides, they do not fully dissolve into the matrix during solution treatment, and the strengthening phases that precipitate during aging tend to over-age further during service, making aging treatment unsuitable. Cold-rolled strip is one of the common products of GH5188 alloy. The alloy raw material is smelted into ingots, then undergoes homogenization, cogging forging, hot rolling, multiple passes of cold rolling, and intermediate annealing, finally delivered in the solution-treated condition.

GH5188 Chemical Composition

GH5188 Mechanical Properties:

GH5188 Thermal Fatigue Performance

The initial melting point temperature range of the alloy is 1200～1210°C, with the initial melting phase being M23C6. After a homogenization process of 1180°C×20h, the eutectic structure is eliminated, dendritic segregation is reduced, and a more uniform microstructure is obtained.

After heat treatment at 1160°C×1h, the as-rolled microstructure experiences rapid grain growth, during which the M23C6 in the alloy dissolves into the matrix and disappears.

At low temperatures, thermal fatigue cracks propagate along the carbide interfaces, while at high temperatures, cracks extend by the interconnection of oxidation pores. Prolonged holding at the upper cyclic temperature limit at high temperatures facilitates the formation of a dense oxide layer, improving the alloy's thermal fatigue performance. However, excessive holding time leads to the formation of numerous oxidation pores on the surface, reducing fatigue performance. Heat treatment at 1175°C×75min+1000°C×8h can delay crack initiation with almost no effect on crack propagation rate. The above is an introduction to GH5188 cobalt-based alloy material.

Available in various specifications including plates, bars, strips, wires, discs, ring blanks, and ring forgings. Bars are supplied in forged-rolled condition, surface ground or turned; discs and ring blanks are supplied in forged condition; rings are supplied in solution-treated condition; plates are supplied after solution treatment, alkali-acid pickling, straightening, and edge trimming; strips are delivered cold-rolled, solution-treated, and descaled; wires are supplied in solution-pickled coil or straight form, or solution-treated straight fine-ground condition.