Hardness Testing Services

Scope

Hardness testing involves determining the indentation hardness of metals, polymers, elastomers, and ceramics using the method appropriate to the material and application, with results reported on the relevant hardness scale.

The principal methods within the scope are:

• Rockwell hardness (ASTM E18) – depth-of-penetration method using diamond Brale or ball indenters across multiple Rockwell scales (HRC, HRB, HRA, and others), suited to the full range of steel and metal hardnesses
• Brinell hardness (ASTM E10) – ball indenter at high load; the large indent gives an average hardness suitable for coarse-grained metals, castings, and forgings; reported as HBW
• Vickers hardness (ASTM E92 / E384) – square pyramid diamond indenter; a continuous scale from very soft to very hard; used for all metals and for microhardness at low loads
• Knoop microhardness (ASTM E384) – elongated pyramid diamond; very low loads for very thin specimens, brittle materials, coatings, and elongated case-depth profiles
• Shore durometer (ASTM D2240) – spring-loaded indenter for elastomers (Shore A) and harder rubber/plastics (Shore D); a measure of indentation resistance for non-metallic materials
• Hardness traverse and case depth profiling – a series of Vickers or Knoop indentations across a cross-section to map how hardness varies with depth, characterising case-hardened, carburised, nitrided, or induction-hardened layers

Applications

• Heat treatment verification – confirming that metals have been heat treated to the correct hardness, whether through quench-and-temper, carburising, nitriding, or annealing
• Incoming material acceptance – verifying that received metal bar, sheet, or forgings meet the hardness specification before processing
• Case depth measurement – profiling the hardness through the cross-section of case-hardened or surface-treated components to confirm case depth and gradient
• Weld and HAZ characterisation – hardness traverses across welds and heat-affected zones to identify hard zones, assess the effect of the weld thermal cycle, and detect over-hard regions prone to hydrogen cracking
• Coatings and thin layers – Vickers and Knoop microhardness testing of electroplated, thermal spray, and hard coatings where only a thin layer is to be characterised
• Castings and forgings – Brinell hardness for large-grained castings and forgings where the Brinell’s larger sampling area is more representative
• Rubber and elastomers – Shore A and D durometer hardness for elastomeric seals, O-rings, gaskets, and polymer compounds
• Ceramics and brittle materials – Vickers and Knoop at appropriate loads for hard ceramics where Rockwell would crack the specimen

Benefits

• Fast, practical, and near-non-destructive – a hardness test leaves only a small indentation and takes seconds, making it suitable for 100% inspection or frequent sampling in production
• Correlates with tensile strength – for steels, established correlations between hardness and tensile strength allow hardness to be used as a rapid proxy for strength verification
• Right method for every material – the range from Shore durometer for elastomers through Rockwell and Brinell for metals to Vickers/Knoop for coatings and ceramics means an appropriate hardness scale exists for any material
• Case depth profiling is fast and informative – a microhardness traverse is a practical way to characterize surface hardening depth, confirming that case-hardening processes met their specification
• Supports weld and heat-treatment QC – hardness surveys are a routine, low-cost check on whether welding and heat treatment have produced the intended metallurgical condition
• Scales are interconvertible – established conversion tables (ASTM E140) allow hardness values on different scales to be compared, which is useful when specifications reference a different scale than the test