Zetium - Analysis of Ni coatings on steel using Stratos

This study demonstrates the powerful capabilities of a Zetium, combined with the Stratos module for determining the mass thickness of nickel coatings on steels. This is achieved using only two bulk standards instead of costly in-type standards.

An important application of Stratos is the analysis of nickel coatings on steel. Nickel coatings are extremely useful in the automotive industry because of the hardness of the layer. Nickel coatings protect the steel from scratching thereby improving wear resistance and extending the life of steel. Nickel coatings are also used for decorative purposes. 

Zetium 

Introduction

Stratos is an evolution of PANalytical’s market-leading thin film metrology software used in the semiconductor industry. A distinct feature of Stratos is the ability to analyze thin layers by using only bulk standards in the calibration. By doing so, one reduces the dependence on standards that are layered samples, which are often difficult to obtain or certify. Whenever available, layered standards and certified reference materials can still be added for ultimate accuracy. Stratos also makes use of a step-by-step setup guide called the Virtual Analyst which simplifies and optimizes the setup of an application. It suggests the best possible measurement conditions for a specific sample type which can be a tedious and complicated process if done manually.

An important application of Stratos is the analysis of nickel coatings on steel. Nickel coatings are extremely useful in the automotive industry because of the hardness of the layer. Nickel coatings protect the steel from scratching thereby improving wear resistance and extending the life of steel. Nickel coatings are also used for decorative purposes.

This study demonstrates the powerful capabilities of a Zetium, combined with the Stratos module for determining the mass thickness of nickel coatings on steels. This is achieved using only two bulk standards instead of costly in-type standards.

Instrumentation

This study was performed using a Zetium wavelength dispersive XRF spectrometer. It was configured with a 2.4 kW Rh anode, SST R-mAX tube and is a fully integrated system with a X-Y sample handler and state-of-the-art SuperQ software, featuring an advanced Fundamental Parameters algorithm. Zetium is engineered for excellence in terms of both analytical accuracy, precision and operational performance.

Sample description and sample preparation

Two nickel on steel samples (NIST certified reference materials) were analyzed in this study (as shown in Figure 1). The samples were fitted into a sample cup with a 27 mm aperture and were measured for a total of 90 seconds.

Figure 1. Cross section of the coating on steel substrate

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Calibration with the Virtual Analyst

Based on the expected thickness and composition of the unknown samples, PANalytical’s Virtual Analyst facilitates the setup of the optimum measurement program to analyze multilayer samples. Optimum XRF lines are chosen based on the existing hardware configuration of the instrument.

Figure 2 shows the theoretical intensity profiles of the possible XRF analysis lines generated using the Virtual Analyst. The plot shows the theoretical intensities of the Ni lines (Kα12 and Lα1,2) with respect to increasing layer thickness of the nickel.

For this application, where layer thickness ranges from 3 - 18 μm, Ni Kα is the optimum line for the analysis. The calibration was set up using only bulk samples – an

Omnian standard in the form of a pressed powder and a solid NiFeCo metal. Both setup samples are secondary standards developed by PANalytical.

Figure 2. Theoretical intensity profile simulation generated by the Virtual Analyst 

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Results and discussion

The obtained XRF results using bulk standards are compared with the certified values. The results reported in Table 1 show that Stratos is capable of analyzing multilayer samples with excellent accuracy using just bulk standards in the calibration.

Table 1. Comparison of certified values and calculated values

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In order to evaluate the instrument repeatability, the same samples were analyzed twenty times sequentially, with loading/unloading between each measurement. The results are reported in Table 2 and shows excellent repeatability of this instrument.

Table 2. Results of twenty repeat measurements of Ni on steel samples

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Conclusion

This data sheet demonstrates that Zetium, in combination with Stratos software is capable of performing accurate analysis of layer thicknesses of Ni coatings on steel. Excellent correlation of Stratos results and NIST standard values shows that for this application, the need for in-type layered standards is unnecessary, which is seen as a significant advantage. The method established by using the Virtual Analyst is fast and permits the automatic selection of optimal measurement conditions for the analysis of thin films and multilayer samples.

The repeatability of the instrument also demonstrates that the combination of Zetium and Stratos is an excellent solution in the production control ofbNi coatings in the steel industry.

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