What Is Surface Integrity?

Complete surface without bumps and burrs

Surface integrity

Surface integrity refers to the surface texture and metallurgical quality of the surface layer after the part is processed, also known as the surface layer quality.

Surface texture mainly includes

Surface metallurgical quality mainly includes microstructural changes,

The analysis of aircraft accidents and failures shows that most of the fatigue damage originates from the surface of or close to the surface of aircraft parts with high working stress, complex shapes, and poor working conditions. This problem was not recognized at first. Design and repair personnel simply choose high-strength materials or increase the cross-sectional area of the part. This not only increases the cost and weight, but also cannot prevent accidents at all. Most of the important stress parts are made of high-strength or high-temperature materials (including various high-temperature alloys, titanium alloys, high-strength alloy steels, etc.). The quality of the surface layer when subjected to repeated loads and erosion of corrosive media under high-temperature and high-speed conditions Seriously affect the reliability and service life of such parts.

The cutting process can affect the surface integrity of the final finished part, which can eventually lead to deformation of thin-walled parts or reduce the fatigue life of critical rotating parts (disks and shafts).

The combined effect of cutting force and the high temperature formed during processing can cause changes in the microstructure of the part, which in turn can cause microhardness, plastic deformation at the grain boundaries, and changes in residual stress under the surface of the part.

Burning of aircraft landing gear parts during grinding processing; Grinding cracks of turbine blades of nickel-based cast alloy engine turbine blades; Part distortion and fatigue strength reduction caused by residual tensile stress on the surface layer after cutting; chloride-containing cutting fluid Weakening of the titanium alloy's resistance to stress abrasion; brittleness caused by chemical absorption of hydrogen, oxygen and other elements during processing; reduction of fatigue strength caused by recasting of the surface in EDM or laser processing, etc. Various light finishing processes are widely used in aircraft production to improve the surface layer quality of important parts of the aircraft. Commonly used processing techniques include abrasive particle flow processing, shot peening, roller calendering, honing, low-stress grinding, electrochemical polishing, and vibration stress relief.