US 2026/0219022 A1Published application

Method and sensor assembly for measuring the thickness of at least one coating layer

AssigneeTata Steel Ijmuiden B.V.

InventorsFrenk VAN DEN BERG, Maria Begoña SANTILLANA DE VEERMAN, Haibing YANG

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Abstract

Method and sensor assembly for non-destructively measuring thickness of a coating layer formed on a workpiece substrate, wherein a first coating layer made of an electrically conductive and either diamagnetic or paramagnetic material is optionally disposed on top of a second coating layer made of ferromagnetic material. The method including placing an inductance sensor head close to the workpiece; measuring inductance at a plurality of frequencies within a frequency range to obtain an inductance spectrum, and measuring the inductance at a predetermined frequency in the lower third of the frequency range or below the lower limit of the frequency range; determining characteristic frequency from the inductance spectrum, which is the frequency at which the phase angle of the inductance is −90°; calculating first coating layer thickness from the characteristic frequency; and calculating second coating layer thickness from inductance at the predetermined frequency and the calculated first coating layer thickness.

Claims19

Dependent claims

A method for non-destructively measuring the thickness of at least one coating layer formed on a substrate of a workpiece, wherein the workpiece comprises optionally a first coating layer made of a material which is electrically conductive and either diamagnetic or paramagnetic, and which is disposed on top of a second coating layer, which is made of a ferromagnetic, ferrimagnetic or anti-ferromagnetic material, wherein the second coating layer is disposed between the first coating layer and the substrate, the method comprising the steps of:

(a) placing an inductance sensor head in close proximity to the workpiece;
(b) measuring the inductance at a plurality of frequencies within a frequency range to obtain an inductance spectrum, and measuring the inductance at a predetermined frequency which is in the lower third of the frequency range or below the lower limit of the frequency range;
(c) determining a characteristic frequency f0 from the inductance spectrum, wherein the characteristic frequency f0 is (c-i) the frequency of the zero-crossing of the real part of the inductance, or (c-ii) the frequency at which the imaginary part of the inductance is at a minimum, or (c-iii) the frequency at which the phase angle of the inductance is −90°;
(d) calculating the thickness t1 of the first coating layer from the characteristic frequency, wherein the thickness may also be zero;
(e) calculating the thickness t2 of the second coating layer from the inductance at the predetermined frequency and the calculated thickness t1 of the first coating layer.

2 more elements

A sensor assembly for non-destructively measuring the thickness of a coating layer formed on a substrate of a workpiece, the substrate having optionally a first coating layer made of an electrically conductive and either diamagnetic or paramagnetic material, which is disposed on top of a second coating layer made of a ferromagnetic, ferrimagnetic or anti-ferromagnetic material, wherein the second coating layer is disposed between the first coating layer and the substrate, the sensor assembly comprising:

at least one sensor head comprising at least one coil, wherein the at least one coil is adapted to generate an alternating magnetic field at a plurality of frequencies within a frequency range, and to sense the change in magnetic field caused by the presence of the workpiece close to the sensor head;
an impedance analyzer adapted to determine the inductance at the plurality of frequencies to obtain an inductance spectrum, and to determine the inductance at a pre-determined frequency which is in the lower third of the frequency range or below the lower limit of the frequency range;
a data processing unit adapted to determine a characteristic frequency from the inductance spectrum, wherein the characteristic frequency is the frequency of the zero-crossing of the real part of the inductance, or the frequency at which the imaginary part of the inductance is at a minimum, or the frequency at which the phase angle of the inductance is −90°;
calculating the thickness of the first coating layer from the characteristic frequency, wherein the thickness may also be zero;
and calculating the thickness of the second coating layer from the inductance at the pre-determined frequency and the calculated thickness of the first coating layer.

2 more elements

Dependencies are inferred from the claim text.