Detection of residual metal stresses with X-ray diffraction
X-ray Diffraction
X-ray diffraction, what is it?
X-ray diffraction is a little-known technique that allows the detection of residual stresses and the determination of the residual austenite content in metallic samples.
Residual stresses
Residual stresses are due to heat treatments, mechanical machining, welding and surface treatments undergone by the pieces during the manufacturing process.
These tensions significantly influence the resistance, especially to fatigue, of the pieces and are often the cause of breakages that have no metallurgical justification.
Induced alterations of the surface tension state
An example are the alterations in the surface tension state induced by grinding burns, which are also easily detectable with X-ray diffraction or with the Barkhausen Noise method.
As regards residual austenite, its presence, even in small percentages (5%), can cause deformations that make the piece unusable. An example is ball bearing races and injector needles for diesel engines. The detection of their presence allows you to optimise heat treatments.
The equipment used by 2 Effe Engineering for the measurement of residual stresses and for the determination of residual austenite allow the completely non-destructive analysis of samples of any size and also allow measurements in the field. For example, Eng. Marconi carried out the measurement of the tensions, caused by casting and mechanical processing, on the cable lugs of the bridge over the Störebealt in Denmark.
Main
Applications
- determination of the quantity of residual austenite on bearings and parts of injectors for diesel engines
- detection of residual stresses on gear wheels
- detection of residual stresses on automotive engine parts (camshafts, connecting rods, crankshafts, rocker arms)
- relief of residual stresses induced by deep drawing (housewares and structural parts
- detection of existing tensions in operation on gas pipelines
- detection of tensions in operation on large tensile structures measurement of the efficiency of shot peening and rolling treatments on components subjected to fatigue
- detection of residual stresses in castings (parts of cast iron machine tools and aluminium automotive castings)
- detection of voltages induced by welding (laser and electron beam)
- research of a correlation between residual stresses and fatigue resistance of aluminium alloy car rims
- optimization of machining parameters for chip removal to improve the fatigue resistance of mechanical components
- detection of residual tensions on helical and leaf springs
- search for critical areas resulting from the application of operating loads (armouring and aeronautical sectors)
A particular application of XRD technology is to quantitatively detect the presence of the different crystalline phases of materials thanks to a greater analysis spectrum. In some cases, it is of fundamental importance to identify which crystalline phases are present in the material as these influence, sometimes heavily, its functional characteristics.
This technique allows 2 Effe Engineering to verify the correct composition of HVOF coatings.
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