Development of Laser Cladding Stellite F Alloy On Valve Face

The results of area scanning of Fe element reveal that theboundary between the laser cladding layer and thesubstrate is clearer and the effect of subsrate compositionson the laser cladding layer is very small (see Fig.6).However the bead welding layer was much affected by thesubstrate composition (see Fig.7).The results are consistentwith that obtained in energy x-ray dispersive analysis (seeFig.4 and Fig.5).Endurance timeEngine powerMaximum torqueMinimum fuel consumption1000 Hs.232.9-244.2 KM1245-1302 Nm.197.8 g/kw.hAfter the engine endurance test was finished, the testedexhaust valve were dissembled and examined. Theexamination results indicated that the wear resistance ofthe laser cladded exhaust valve is very well, the wearingvalue is 25%~62.5% as low as normal wearing value. Thefailure problems of erosion, peeling and cracking did notbe discovered in tested valve faces. It demostrates that thelaser cladded exhaust valves have good properties andexcellent performances in high power diesel engines andthe laser claddding process is successful in application ofexhaust valve faces.CONCLUSIONFig.6 Area scanning of Fe of LC layer1. The cladding layer with fine crystalline grain and closemicrostructure has been obtained in valve face by lasercladding stellite F alloy2. The laser cladding process has the advantage of lowerdilutability in cladding layer, so it can decrease thethickness of cladding layer and cut down cladding materialexpenses.3..Higher microhardness and more reasonablemicrohardness distribution in cladded layer can beproduced by laser cladding process. The microhardness ofthe laser cladded layer is above 600 kg/mm 2 , HV 0.2 100higher than microhardness of bead welding layer at samedepth.Fig.7 Area scanning of Fe of BW layerBecause the density of laser power is higher and the timeof laser action is shorter in laser cladding process,theenergy less in heating process is lower, the range of heateffect is smaller also, and then the molten capacity of thesubstrate and the action of dilution to cladding layerbecame smaller. From above-mentiened reasons thecompositions required for assured properties can beobtained in the thinner laser cladded layer and theexpensive cladding materials can be saved. The lasercladding process is a better process than the bead weldingfor enhancing the valve face.ENGINE ENDURANCE TESTThe engine endurance test for the exhaust valve with lasercladding stellite F alloy was conducted in a WD 615-68high-performance test engine. The detailed test conditionsare as following:4. The performances of the laser cladded layer on valveface completely meet the needs of high performanceengines. The laser cladding process is a potential processin surface enhanced techniques for exhaust valve face.REFERENCES[1] Qixian Shen, Heavy Duty Truck, 22(1994)2,P7-12[2] Qixian Shen, Heavy Duty Truck, 23(1994)3,p5-9[3] Zhengzhong Guan etc, Proceedings of NatinalConference on Science and Technology of Laser Layer,p5-23, Shen Yang, China,1991[4] Automotive Engineer, 16(1991)4,P70[5] Yan shen, Qixian Shen, Heavy Duty Truck, 25(1994)54