Fundamentals of Advanced Coatings

Analyze coating failure mechanisms, including cracking and spalling, across uncoated, coated, and prematurely failing cases; compare wear rates, coating thickness, and substrate hardness to extend lifetime.

Explore coating composition with nitrides, carbides, and oxides deposited by pvd or cvd, noting high hardness and a friction coefficient of 0.4–0.9, and consider molybdenum sulfide or diamond-like carbon.

Tribological coatings deliver specified friction behavior and high wear resistance by controlling roughness, thickness, composition, microstructure, and residual stress to maximize load carrying capacity and prevent premature failure.

Examine Hertzian and asperity contact stresses in non-conforming and conforming contacts; reveal subsurface shear-driven cracking and how coatings affect wear, friction, and load carrying capacity.

Evaluate strategies to improve load bearing capacity at contact surfaces. Use thick thermochemical coatings to spread stress and boost capacity, though wear resistance remains limited.

Explore coating structures from single component to multi-component, gradient, multilayer, superlattice, and duplex treatments, and learn how nanocomposites enable metastable materials and supersaturated solutions.

Explore graded coatings that gradually transition from a ductile substrate to a hard coating, reducing interfacial stress through nitrided and carburized profiles created by reactive sputtering in PVD.

Explain how duplex coatings combine a substrate, an intermediate layer, and an external PVD layer to maximize wear resistance and load-bearing capacity.

Understand multilayer coating architecture with a metal base on a substrate and alternating titanium nitride and aluminum nitride layers deposited by sputter or arc methods, enhancing hardness and wear resistance.

Superlattice coatings stack alternating materials with similar crystal structures with lattice constants, bilayer periods of 2–10 nm; interfaces hinder crack propagation and yield hardness to 40 GPa with friction 0.4.

Explore nanocomposite coatings formed by nanometric particles dispersed in an amorphous matrix, enabling a two-phase, spontaneously separated structure with high hardness around 50 gigapascal and crack resistance.

Explore diamond like carbon (dlc) coatings, an amorphous blend of diamond and graphite structures that yields high hardness, wear resistance, chemical inertness, and solid lubrication, formed via energetic particle bombardment.

DLC remains metastable at ambient conditions, graphite being the stable structure; heating releases hydrogen, forms graphite, and reduces hardness, with high hardness and low friction only below four degrees Celsius.

Identify residual stresses in PVD and CVD coatings from deposition and cooling. Evaluate them with X-ray diffraction and substrate curvature using the Stoney equation.

Understand how cooling creates thermal stresses in coatings, distinguish intrinsic growth stresses from thermal ones in pvd and cvd, and how deposition temperature and ion bombardment shape residual stress.