Abstract:
Electrodeposition of martensitic Fe-C and Fe-Ni-C alloy coatings was carried out
hom sulphate based batbs at room temperature. The baths contained various
amount of citric acid (0.2 to 10 gill and L-Ascorbicacid 10.2 to 10 gill and in
some cases additives viz. gelatin 10.2to I gil),sodium lauryl sulphate 10.5gil) to
observe their influences.on the morphology and mechanical properties of the
coatings_
Chemical analysis showed the carbon content of both Fe.C and Pe-Ni-C alloy
deposits to be above I% and Ni content of Fc-Ni.C alloy deposit within 4-6%.
It was observed that the carbon content of the Fe-C deposits becomes less
sensitive to CA and LAAcontent of the bath as higher amounts of CA and LAA
are added. Structure of the deposit was examined by optical microscopy and xray
diffractometry. The microstructure of as-deposited etched sample was dark
and difficult to observe under a microscope,but the annealed structure showed a
structure similar to annealed carbon steel. X-ray diffraction pattern of asdeposited
Fe-I.1%C alloys suggests these to be rnartensitic in structure.
Mechanical properties of these coatings viz. microhardness, ductility, wear
resistance were investigated in relation to the prcscnce of additives like gelatin
and sodium lauryl sulphate in the bath and post-deposition heat treatment. Fe-C
alloy deposited from bath containing 10 gil CA and 10 gil LAAshowed hardness
as high as 790 HV, whereas the deposits hom other baths showed relatively
lower bardness values such as 701, 386 HV. It was found that as the percentage
of CA and LAA in the bath decreases, hardness of the deposit also decreases.
Tempering of the as-deposited Fe-1.1%C alloy at 2000C lor half an hour does
not cause any appreciable decrease in hardness. However, gelatin was found to
have a significant role on bardness; as the gelatin content in the bath increases,
the corresponding hardness decreases.It was found that presence of gelatin in the
baths and tempering of the deposits cause considerable improvement in
ductility. FeA.3%Ni-1.1%C alloy showed better ductility than as deposited or
tempered Fe-I.l %C alloy.
