Cause and Control Method of Cracking in Electroplated Hard Chrome Area on Surface of 30CrMnSiNi2A Steel Axle

When the unserviced 30CrMnSiNi2A steel axle was stored for a period of time, cracks appeared in the electroplated hard chrome area on surface of the axle. The surface cracking cause of the axle was studied by morphology observation, chemical composition analysis, microstructure observation, mechamical property analysis and hydrogen content and residual stress testing. The measures to control cracking were proposed. The results show that the hydrogen-induced delayed cracking (hydrogen embrittlement) of the axel occurred by the synergistic effect of the hydrogen diffused in surface of the axle during electroplating hard chrome and the tensile stresses introduced during grinding of the hard chrome layer. By the measures of the improvement of electroplating process, removing hydrogen in time after electroplating, modifying the grinding process of the electroplated layer and increasing stress relief annealing procedure, no cracking occurred in the axle.