Effect Of Double Pulse Current Parameters On Delay Crack Of Chrome Layer

Aiming at the delayed cracks of chromium plating technology on30CrMnSiA alloysteel,15-5PH（0Cr15Ni5Cu3Nb）and1Cr11Ni2W2MoVA stainless steel used on aerosealcomponent for undercarriage, this paper mainly studied the effect of dual pulse currentparameters for the delay crack of chromium plating with standard electroplating bath.Set temperature at55±1℃and90minutes for the dual pulse electroplating processparameters provisionally; According to the experience set the dual pulse process parameterswith dual pulse frequency at50～150Hz,reverse current density is equal to the forwordcurrent density at50～70A/dm~2,duty cycle at60～80%.Ameliorated pulse process parameterswith the orthogonal experiment,studied effect of pulse frequency,current density and dutycycle for the delay crack of chromium plating.As a result current density is the most mainlyfactor affect the delay crack of chromium plating. In the case of the same other conditions,theamounts of delay crack increased when current density raise.The amounts of delay crack isleast when pulse frequency at100Hz, duty cycle at70%.Synthesize the data analysis of theorthogonal experiment and the result of coating’s delay crack tests, educed dual pulse processparameters after optimization as: dual pulse frequency at100Hz,current density at50～70A/dm~2,duty cycle at70%.Changed the temperature for electroplating experiment on the base of optimization pulseprocess parameters, temperature parameters range as50℃、55℃、60℃.Study the amountsof delay crack with the derect current and unidirectional pulses current plating on the samecurrent density,temperature and electroplating time.As a result the amounts of delay crackwith dual pulse is less than the derect current and unidirectional pulses.In study with the different of the amounts of delay crack of the coating intemperature-change experiment. Educed optimization dual pulse process parameters for30CrMnSiA alloy steel,15-5PH（0Cr15Ni5Cu3Nb）and1Cr11Ni2W2MoVA stainless steel.As follows:temperature55℃,current density at50～60A/dm~2, dual pulse frequency at100Hz,duty cycle at70%,electroplating time is madding for need with standard electroplatingbath.This pulse process parameter is the same with these three materials hereinbefore withbeautiful appearance,the amount of delay crack is least.