Slide 1
Change the surface without replacing the bulk
A coating gives a component a surface layer with selected properties. The underlying material can still provide most of the structural strength.
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Wear resistance, corrosion protection and thermal behaviour require different coating systems. A layer optimized for one duty may be unsuitable for another, so coating is a category rather than one universal treatment.
Slide 2
Preparation makes adhesion possible
The surface must be suitable for the coating to attach. Contamination, loose material and unsuitable texture can weaken the interface.
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Surface preparation can involve cleaning, roughening or chemical treatment. The correct method depends on both substrate and coating; making every surface as rough as possible is not a general solution.
Slide 3
Thickness has an operating range
Too little coating may leave inadequate coverage. Too much can create stress, cracking or dimensional problems depending on the system.
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Edges and recesses may receive different thicknesses from broad flat regions. Inspection should therefore consider geometry rather than relying on one convenient measurement point.
Slide 4
The layer must tolerate movement
Coating and substrate can expand differently with temperature or deform differently under load. Their interface must accommodate those differences.
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A hard layer on a flexible base can crack if the base bends too much. Useful performance depends on the combined system, not simply the coating’s hardness measured separately.
Slide 5
Protection needs continuing assessment
Wear, impact and environmental exposure can damage a coating during service. Repair and inspection plans preserve the intended surface function.
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Small defects may allow corrosion to spread under a barrier layer. Detecting loss of adhesion or underfilm attack can matter before a large visible patch has detached.