Heat Treatment-Driven Structural and Morphological Transformation Under Non-Parametric Tests on Metal–Ceramic-Sputtered Coatings

Abstract

The present study analyzes experimental data using qualitative and quantitative methods to identify significant statistical changes. These methods were employed to evaluate the results from the structural characterization of annealed TiWN and TiWC coatings elaborated by magnetron sputtering. The as-grown coatings were thermally treated at 500 °C in a furnace under an Ar atmosphere. Structural characterization was performed by X-ray diffraction and optical and electronic microscopy. The chemical composition was determined by energy dispersive X-ray spectroscopy. The data were analyzed using the Kruskal–Wallis (K-W) and Spearman correlation tests as non-parametric methods, employing free statistical software. The response variable—the crystallite size calculated through the Scherrer formula—is statistically tested. The data of the crystallite size of each sample were forecasted using the simple moving average (SMA) method to increase the number of data points of each sample to 12. The crystallite size of each sample remained unchanged before and after thermal treatment. However, microscopy analyses revealed strong surface cracking. The average crystallite size before and after the thermal treatment was analyzed by the K-W correlation, revealing significant changes considering a reliability level of 95% and a significance error of 5%. The analysis revealed a strong correlation between experimental data and statistical treatment results.