PLASMA NITRIDING TREATMENT FOR IMPROVEMENT OF FATIGUE STRENGTH OF STEEL ENGINE PARTS

One of the main tasks in the process of designing engine components is to determine safety against critical stresses, i.e those stresses which cause unwanted elastic and plastic deformation or fracture. The application of surface heat treatment of engine components can considerably increase their fatigue and decrease the material share of the final parts. All surface treatments harden the surface and produce volume changes in the surface layer, and these increase the fatigue strength. Nitriding has the advantage that it minimizes unvoidable distortions. Plasma nitriding is one of the most up-to date surface treatments processes. Wohler rotating-bending fatigue testing has been used to study the fatigue behaviour of plasma nitriding steel specimens for crankshafts. Test results show that plasma nitriding improved the fatigue bending stress limit by a factor of 1.5 and the endurance curve exponent by a factor of 2.