1. What Wear Rate Means
Wear rate expresses the amount of material removed from a surface during a defined amount of friction work, time or sliding distance. For wear-resistant steel plate, the wear rate is not a single fixed property: it depends on the wear mechanism (abrasive, adhesive, erosive or impact wear), the load, the sliding speed, the hardness of the abrasive, the surface condition and the test geometry. A wear rate value is therefore only meaningful together with the test conditions under which it was measured. Comparing plates from different suppliers should be done with identical test procedures, for example the standard pin-on-disc or dry sand rubber wheel tests where they apply.
2. Method 1: Wear Intensity (Material Loss per Unit Time and Load)
The first common method defines the wear rate as the amount of wear under a unit load in a unit time:
I = dV / (dt x dF)
where V is the volume of material worn away, t is the friction time and F is the applied load. This definition suits steady-state wear tests where both time and load are controlled, such as pin-on-disc tests with a constant normal force. The result is typically expressed in volume per unit time per unit load, and it allows the wear behaviour of two materials to be compared at the same load and sliding conditions.
3. Method 2: Volume Wear Rate per Unit Friction Work
The second method expresses the wear rate as the volume of the worn sample divided by the cumulative friction work:
delta = V / SigmaW = H x A / SigmaW
where delta is the wear rate in cubic centimetres per newton-metre (cm3/(N x m)), V is the specimen wear volume in cubic centimetres, H is the total linear wear of the sample in centimetres, A is the apparent contact area of the sample in square centimetres, and SigmaW is the cumulative friction work in newton-metres. This definition is common in laboratory wear testing where the friction force is recorded throughout the test, and it directly relates material loss to the energy consumed by friction. A similar volume-based formula appears in some national standards for wear testing; the standard edition applicable to the product should be confirmed before quoting values.
4. Method 3: Mass-Loss Method
The third common method uses the mass difference of the specimen before and after the test:
A = deltaW / (rho x S x P)
where deltaW is the mass difference in grams, rho is the density of the steel in grams per cubic centimetre, S is the friction distance, and P is the applied load. Because the mass loss is easy to measure with a laboratory balance, this method is widely used in field and workshop comparisons. The mass loss is converted to a wear rate by dividing by the density, distance and load, which makes results comparable between specimens of the same steel. For wear-resistant plates, the density of steel can be taken as approximately 7.85 g/cm3 unless the alloy differs significantly.
5. Relative Wear Rate and Choosing the Right Method
The relative wear rate is the ratio of the wear rate of the test material to the wear rate of a standard reference material under the same conditions. It is a convenient way to report improvement, for example when a candidate wear plate is compared with a mild steel reference. The choice of calculation method should follow the test standard and the available measurements: use Method 1 when time and load are controlled, Method 2 when friction work is recorded, and Method 3 when only mass loss, distance and load are available. Regardless of the method, the conditions must be documented so that the numbers are reproducible and comparable.
Frequently Asked Questions
Which wear rate method should I use? It depends on the data you can measure. Use the time-load method when the test duration and load are controlled, the friction-work method when friction force is recorded during the test, and the mass-loss method when you can only weigh the specimen before and after.
What is the unit of the volume wear rate? In the friction-work definition, the wear rate is expressed in cubic centimetres per newton-metre (cm3/(N x m)), where the wear volume is divided by the cumulative friction work.
How do I measure the wear volume? The wear volume can be calculated from the total linear wear multiplied by the apparent contact area, or derived from the mass loss divided by the density of the steel (about 7.85 g/cm3).
What is relative wear rate? It is the ratio of the wear rate of the test material to that of a standard reference material tested under identical conditions; a value above 1 means the test material wears slower than the reference.
Can I compare wear rates from different suppliers directly? Only if the test conditions are identical: same wear mechanism, load, speed, abrasive and measurement method. Wear rate is condition-dependent, so numbers from different procedures are not directly comparable.
Is the mass-loss method accurate for wear plates? It is accurate when the mass difference is large relative to the balance resolution and when the density is known. For thin plates and short tests the mass loss may be too small, and a volume-based method is preferable.
