AISI 4140 alloy steel is defined as a low alloy steel which has 1% Cr-Mo as strengthening alloy elements.Compared with AISI 4130, it has a higher carbon content with good balance of strength, toughness ,abrasion and impact resistance and heat treatment capabilities,but poor in weldability characteristics.AISI 4140 is generally supplied in quenched and tempered condition with hardness 28-32HRC.