The influence of pressure on mechanical properties for specimens treated by pressurized $NH_3$ gas nitriding method has been studied. The material used is SCM4 and A13l-B. Two different pressure conditions, 3.5 and 7 kgf/㎠, are tested, and for each pressure condition, 3 different treatment times are selected, while are treating temperature and gas composition held constant.
Rotary bending fatigue and pin-on-disk wear tests are made. It is found that the specimens treated under higher pressure show consistently higher values for hardness, fatigue life and wear resistance, as compared with those under lower pressure. This is believed to be due to the increased amount of activated nitrogen for higher pressure case.
As the treatment time is increased, the property values are also increased, although this increase becomes dull. Friction coefficient is observed to be reduced for longer treatment time and higher pressure. When compared with the conventional $NH_3$ gas method, the pressurized gas method has provided distinctly improved mechanical properties.
