QUALITY IMPROVING OF LOCAL SPROCKETS USING THE PACK CARBURIZING METHOD WITH HOLDING TIME VARYING

Sprockets are spare parts on motorbikes that work by transmitting power to the rear tire of the motorbike. Various sprocket products are sold on the market, ranging from standard original products from Japanese manufacturers which are quite expensive to locally made ones with relatively cheap prices. In order to compete with Japanese manufactured sprocket products, it is necessary to improve the mechanical properties of localsprockets so that the quality of local sprockets approaches or exceeds Japanese manufactured sprockets, but at a low price. This research aims to produce locally made sprockets so that the quality can approach or exceed original Japanese manufactured sprockets at a relatively cheap price. The method used for surface hardening is pack carburizing, the carburizing temperature is at 920oC with holding times varying to 15, 30, 45 and 60 minutes. The carbon material used is coconut shell charcoal, then the catalyst used is beef bone (CaCO3) with a ratio of 85% carbon and 15% catalyst. The results of the tests that have been carried out show that there has been an increase in the mechanical properties of the local carburized sprocket as time increases. The 15 minute holding time specimen had a layer thickness of 265.77 μm, a hardness value of 405.84 HV and a wear rate of 360 10-6 gr/minute; the 30 minute holding time specimen had a layer thickness of 346.55 μm, a hardness value of 188.81 HV and a wear rate of 257 10-6 gr/minute; the 45 minute holding time specimen had a layer thickness of 935.47 μm, a hardness value of 277.37 HV and a wear rate of 243 10-6gr/minute; The most optimal specimen with a holding time of 60 minutes has a layer thickness of 452.42 μm, a hardness value of 407.44 HVand a wear rate of 97 10-6gr/minute. These results have shown an increase in the mechanical properties of the specimen so that the quality of local sprockets approaches or even exceeds the quality of original Japanese manufactured sprockets but at a relatively cheap price.