Evaluation of the wear and abrasion resistance of hard coatings by ball-on-three-disk test methods—A case study

Engineered surfaces can provide superior resistance to abrasive and adhesive wear. There are many types of hard coatings readily available including diamond-like-carbon (DLC) coatings, nitrides, carbides, oxides, etc., and due to the many processing alternatives including alloying element, thickness, deposition technique, etc. each of these types contains a virtually endless number of choices. Fundamental materials properties such as hardness and toughness are often not adequate to reflect how a particular coating will perform, and some of these properties, toughness for example, can be hard to measure and are usually not available. In contrast, bench-scale measurements of friction and wear can provide reliable and meaningful data. However, many of these techniques are expensive and time-consuming and determining the best coating to meet the requirements of a specific application amongst this endless variety of materials can be cost-prohibitive. In this case, ball-on-three-disk (BOTD) test methods are used to provide a rapid, cost-effective, and accurate measure of the wear and abrasion resistance of representative samples of many of the types of coatings being designed with modern techniques. This work provides a case study of steel coated with seven types of nitrides, novel Cr and Ni plated coatings, as well as baseline uncoated and manganese phosphate coated steel samples. The data illustrates the value of the BOTD test method as a bench-scale tribological test as well as significant insight to how subtle design features and changes in the testing conditions of coatings can lead to significant differences in performance.