Abstract
The effect of surface integrity on the hot fatigue performance of Ti2AlNb alloy was investigated. A turning process was used to prepare the standard specimens for hot fatigue tests. The surface integrity characterization and axial fatigue tests were performed. The results show that the influence of surface roughness on the hot fatigue performance of the Ti2AlNb alloy is a secondary factor. The compressive residual stress and enhanced microhardness in the surface layer has a significant effect on the hot fatigue life and they are dominant in the hot fatigue behavior of the Ti2AlNb alloy. Through the investigation on the characteristics of the fatigue fractures, the fatigue propagation process was significantly suppressed because of the strong residual compressive stress and microhardness distribution on the surface layer of the Ti2AlNb specimen.
Highlights
The Ti2AlNb intermetallic alloy is a new type of Ti-Al intermetallic compound with ordered orthogonal structure O phase as the main phase composition [1,2], which has high specific strength, good room temperature plasticity, good oxidation resistance, high strength at high temperature, fracture toughness and excellent creep resistance [3–5]
When the residual stress of machined surface is very small, there is a strong relationship between surface roughness and fatigue life of the parts
The texture of wave crests and troughs caused by the increase of turning parameters can be clearly observed
Summary
With the continuous development of the aerospace industry, the performance requirements of materials are increasingly high, especially for aero-engine materials. Relevant data studies have shown that the integrity of the machined surface has an important impact on fatigue life and service performance of the parts [8,9]. Wang et al studied the effect of machined surface integrity on fatigue properties of a nickel-based single crystal alloy. In addition to surface roughness, residual stress distribution has a significant effect on fatigue properties. When the residual stress of machined surface is very small, there is a strong relationship between surface roughness and fatigue life of the parts. The residual compressive stress gradient distribution layer introduced by machining on the surface of the part material can form a “neutralization” effect with the load stress borne by the part during the service of the part, so as to reduce the average load stress, draw up the generation and propagation of fatigue cracks and improve fatigue life [20,21]. In order to express it concisely, the Ti-22Al-23Nb-2(Mo,Zr) alloy is referred to as the Ti2AlNb alloy hereafter in this paper
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