| Sapphire (Single-Crystal Aluminium Oxide) | Watch covers, optical windows, sensor covers, camera lens covers | Excellent
Mohs hardness: approximately 9 | High optical clarity; available in optical-grade polished forms | Excellent resistance to abrasion, many chemicals, and ultraviolet exposure | High-temperature capability; exact limit depends on mounting and coating system | Extremely hard, durable, and stable for demanding precision products | Higher cost; more brittle than many polymer alternatives; difficult to machine | Premium wear surfaces, optical equipment, aerospace and industrial sensors |
| Chemically Strengthened Aluminosilicate Glass | Display covers, control panels, instrument windows, protective glass sheets | Very Good
Surface hardness commonly around 6–7 Mohs, depending on formulation | Excellent transparency and low haze when properly polished | Good resistance to household chemicals and ultraviolet exposure; edge damage can reduce durability | Suitable for normal electronics and indoor industrial environments; thermal shock limits vary by grade | Strong balance of clarity, thinness, impact resistance, and scratch resistance | Can still scratch from hard mineral particles; damaged edges may initiate cracks | Smart devices, vehicle displays, industrial human-machine interfaces, building controls |
| Tempered Soda-Lime Glass | Tabletops, appliance doors, architectural panels, protective covers | Good
Typical glass hardness: approximately 5–6 Mohs | High transparency with low haze in clear grades | Good resistance to many common chemicals and outdoor exposure | Better thermal shock resistance than annealed glass; sudden temperature changes can still cause breakage | Widely available, cost-effective, and stronger than ordinary annealed glass | Less scratch-resistant than sapphire or ceramic; cannot be cut after tempering | Furniture, appliances, construction, retail fixtures, and general protective panels |
| Alumina Ceramic (Aluminium Oxide) | Wear plates, mechanical guides, ceramic windows, protective covers, industrial components | Excellent
Mohs hardness: approximately 8–9 | Opaque in most industrial grades; translucent or transparent grades are available | Excellent abrasion, corrosion, and ultraviolet resistance | Excellent high-temperature stability; usable range depends on purity, geometry, and thermal cycling | Very hard, electrically insulating, and suitable for severe wear environments | Brittle; machining and finishing can be expensive; lower impact tolerance than metals or polymers | Mining, process equipment, electrical insulation, laboratory and high-wear systems |
| Polycarbonate with Hard Coat | Safety eyewear, machine guards, face shields, vehicle lenses, electronic covers | Very Good with Hard Coat
Coated surfaces can reach 3H–6H pencil hardness, depending on coating | High transparency and impact resistance; optical quality depends on coating uniformity | Good when UV-stabilized and properly coated; some solvents can cause stress cracking | Typical continuous-use range is approximately −40°C to 115°C, depending on grade and load | High impact strength, low weight, and easier forming than glass | Uncoated surfaces scratch easily; hard coatings may wear, crack, or delaminate under severe abuse | Transport glazing, protective equipment, industrial guards, outdoor electronics |
| Acrylic (PMMA) with Hard Coat | Display windows, signage, lighting covers, instrument panels, protective sheets | Good with Hard Coat
Coated surfaces commonly reach 3H–5H pencil hardness | Excellent visible-light clarity and naturally low haze | Good weatherability and UV resistance; solvent resistance varies by grade | Typical continuous-use range is approximately −40°C to 80–90°C, depending on grade | Lightweight, highly transparent, weatherable, and easy to fabricate | Lower impact resistance than polycarbonate; uncoated PMMA is relatively easy to scratch | Retail displays, outdoor signage, lighting, consumer products, and equipment panels |
| Hard-Anodized Aluminium | Housings, panels, trims, handles, equipment frames, consumer-electronics enclosures | Very Good
Anodic oxide hardness commonly around 300–500 HV; process-dependent | Opaque; available in natural metallic and dyed finishes | Good corrosion and UV resistance when properly sealed; vulnerable to strong alkaline cleaners | Good thermal stability for normal metal applications | Lightweight, conductive, attractive, and more wear-resistant than untreated aluminium | Surface can be damaged by sharp impacts; color and hardness depend strongly on process control | Outdoor equipment, electronics, transport interiors, architectural hardware |
| DLC (Diamond-Like Carbon) Coating | Machine parts, shafts, gears, tools, automotive components, watch components | Excellent
Hardness commonly about 10–30 GPa, depending on DLC type | Opaque or dark gray in most configurations; thin films preserve substrate geometry | Very good wear and chemical resistance; performance depends on film composition and adhesion | Often suitable for elevated temperatures, but maximum temperature varies by DLC formulation | Low friction, high wear resistance, and thin protective layer | Requires controlled deposition and compatible substrate preparation; coating defects can affect service life | Automotive, precision machinery, medical instruments, cutting tools, and industrial components |
| PVD Titanium Nitride / Chromium Nitride Coating | Cutting tools, decorative hardware, molds, dies, fittings, wear components | Excellent
Typical coating hardness: approximately 1,500–3,000 HV, formulation-dependent | Opaque; TiN is commonly gold-colored and CrN is commonly silver-gray | Good wear and corrosion resistance; exact performance depends on coating chemistry and environment | Suitable for elevated-temperature tooling; service temperature varies by coating type | Thin, hard, decorative, and effective against abrasive wear | Does not repair weak substrates; edge impact, poor adhesion, or excessive thickness variation can cause failure | Industrial tooling, hardware, molds, decorative metal products, and engineered wear parts |
| Silica-Based Sol-Gel or Nanocomposite Hard Coat | Plastic lenses, display films, optical panels, coated plastics, protective sheets | Very Good
Often engineered to reach 4H–9H pencil hardness, depending on formulation and test method | High clarity is possible with controlled particle size and coating thickness | Good abrasion and UV resistance; chemical resistance depends on the binder system | Moderate to good thermal stability; curing and substrate compatibility are critical | Improves the surface durability of lightweight transparent polymers | May crack under flexing; coating adhesion and curing quality are essential | Optical plastics, displays, lighting covers, automotive interiors, and consumer electronics |
| UHMW-PE (Ultra-High-Molecular-Weight Polyethylene) | Wear strips, chute liners, conveyor components, sliding pads, protective films | Good for Sliding Wear
Not a high-hardness surface; valued for abrasion and impact resistance | Usually opaque or translucent; optical clarity is not its primary function | Excellent resistance to moisture and many chemicals; UV stabilization may be required outdoors | Typical continuous-use range is approximately −100°C to 80°C, depending on grade and load | Very low friction, excellent impact resistance, and strong resistance to sliding abrasion | Can deform under sustained load; relatively low stiffness and limited high-temperature capability | Material handling, mining, food-processing equipment, marine systems, and industrial liners |
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