Wear Issues and Anti-Wear Surface Treatments

Wear is a surface-related phenomenon occurring predominantly on the outer surfaces of parts. Wear controls the service life and performance of many moving mechanical components in industrial parts and designs. In most industrial applications, significant financial losses result from accelerated wear of various mechanical components (adhesive, abrasive, corrosive, fatigue, corrosion, erosion, cavitation). Various surface treatment and coating methods are employed to protect materials from wear-related degradation. Coating and surface engineering solutions that extend the service life of parts or products continue to be developed to minimize the effects of mechanical wear. At this point, the selection of coating material and method plays a critical role. The appropriate coating must be selected according to substrate type, part size and surface characteristics, and the coating thickness and application method must be determined. The required properties of the coating should be evaluated based on the operating environment, working conditions, and loads. Figure 1 comparatively presents the approximate thickness of various surface engineering processes. Thick wear-resistant coatings can be obtained through welding-based hard surfacing and thermal spray methods. Thin film coatings can be produced in mono or multi-layer form below 5 microns. Figure 2 presents the surface engineering processes used to prevent wear. Selecting an appropriate technology to produce a specific surface combination is a highly complex process involving multiple properties. Achieving the desired surface characteristics entails a systematic correlation. Generally, the surface treatment selection process includes economic and ecological considerations. Surface technologies are gaining importance as an integral part of production chains. Surface treatments today can generally be applied individually, but can also be integrated into post-processes and process chains. Sixteen criteria are fundamentally used in the selection of surface coatings and surface treatments: (1) Operating temperature, (2) Operating environment characteristics, (3) Contact and loading types, (4) Substrate material properties, (5) Counterface condition, (6) Coating-substrate adhesion strength, (7) Process economics, (8) Surface coating or surface hardness, (9) Process temperature, (10) Part size, (11) Surface treatment depth, (12) Surface treatment homogeneity, (13) Part geometric shape, (14) Surface quality, (15) Pre-treatments, (16) Post-treatment operations. When grouping these factors, coating selection and solution are implemented based on five main design criteria: 1) operating conditions, 2) process conditions, 3) geometric conditions, 4) topological conditions, 5) economic conditions. General Assessment Wear-resistant metallic, ceramic or composite-based coatings can be applied through different methods using semi-automatic or fully automatic systems depending on part geometry and quantity. Performance characteristics are compared based on operating conditions and process cost. The user's coating selection and application method are among the most important criteria. The part's reliability and service life extension depend on coating quality and application success. References • J.R. Davis, Surface Engineering for Corrosion and Wear Resistance, ASM International 2001. • C.M. Cotell and J.A. Sprague, Preface, Surface Engineering, Vol 5, ASM Handbook, ASM International, 1994. • K.G. Budinski, Surface Engineering for Wear Resistance, PrenticeHall, Inc., 1988. • W. Tillmann, E. Vogli, Selecting Surface-treatment Technologies, Materials Science, 2006.  

Associate Professor Ekrem Altuncu Member, TÜYİDER (Association for All Surface Treatment Processes) Scientific and Technical Committee Sakarya University of Applied Sciences Director, Materials and Manufacturing Technologies Application and Research Center - SUMAR