chapter  14
The surface hardening of steels
Pages 11

Many metal components require a combination of mechanical properties which at fi rst sight seems impossible to attain. Thus, bearing metals (see Section 18.6) must be both hard and, at the same time, ductile, whilst many steel components, like cams and gears, need to be strong and shock-resistant, yet also hard and wear-resistant. In ordinary carbon steels, these two different sets of properties are found only in materials of different carbon content, e.g. a steel with about 0.1% carbon will be tough, whilst one with 0.9% carbon will be very hard when suitably heat-treated.