We have studied in this paper the effect of thermal gaseous using NH3 – gas at some
diffusion layers properties of tool steel 20 in temperature range (550 ,650 ,750, 850) 0C ,
4h at each one . The purpose of this heat treatment is to get and determ
ine the microhardness,
fatigue and corrosion resistance.
The micro-hardness was determined using Vickers's tester with values ranged
between ( 130-435 ) HV.
In order to verify these results, we studied the microstructure if the surface layers
using metallurgical microscope and SEM (Scanning Electron Microscope). Furthermore
the corrosion resistance was studied after immersing it in sea water for two year.
