Wear-resistant camshaft and method of producing the same

A high-energy surface remelting method for producing a wear-resistant cast iron camshaft, the method comprising:

• generating a temperature time curve of pre-heating and of the remelting with two different energy sources S1 and S2 with different power densities p1 and p2, wherein the temperature time curve comprises two superposed short-time temperature time cycles T1 and T2;
• and
• pre-heating and remelting the surface in accordance to the temperature time curve,
• wherein the temperature time cycle T1 has a peak temperature T1max of 560° C.≦T1max≦980° C., a heating time of 0.5 s≦t1≦6 s, an average heating speed of (ΔT1maxc/Δt1c) of 90 K/s≦(ΔT1maxc/Δt1c)≦1900 K/s and an initial quenching speed (ΔT1a/Δt1a) of 50 K/s≦(ΔT1a/Δt1a)≦500 K/s and the power density p1 of the energy source S1 reaches the value of 8×102 W/cm2≦p1≦8×103 W/cm2,
• wherein the temperature time cycle T2 has a peak temperature T2max of T2max≧Ts, whereby Ts represents the melting temperature of the cast-iron used, an average heating speed (ΔT2maxc/Δt2c) of 3000 K/s≦(ΔT2maxc/Δt2c)≦40,000 K/s, a solidification speed vs, of the melt of 10 mm/s≦vs≦67 mm/s as well as a power density p2 of the energy source S2 of 0.8×104 W/cm2≦p2≦8×104 W/cm2 is selected,
• a time period t21=t2−t1 after the temperature time cycle T2 begins is 0.3 s≦t21≦11 s,
• a temperature T1min at which the temperature time cycle Tz begins is T1min>500° C.,
• a melting pool life ts is in the range of values from 0.08 s≦Δts≦0.8s, and
• a feed rate vB of the high-energy energy source S2 reaches the value of 600 mm/min≦vB≦4000 mm/min.

A method for producing a high wear resistant cast iron camshaft having a remelted surface layer with a fine dispersed microstructure and an underlying supporting hardening layer, said method comprising:

• a high energy short time pre-heating process of the surface near region produced by an energy source S1 with the power density p1 and a resulting short temperature-time cycle T1;
• a high energy short time surface remelting process produced by a second energy source S2 with a higher power density p2>p1 and a resulting short temperature-time cycle T2;
• a short time period t21, between the end of the short temperature-time cycle T1 and the beginning of the short temperature-time cycle T2;
• and
• a self-quenching of the heated and remelted camshaft.

A wear-resistant cast-iron camshaft having a surface layer comprising:

• at least one ledeburitic remelted layer with a cementite content over at least one martensitic hardening zone;
• the at least one ledeburitic remelted layer comprising finely dispersed ledeburitic cementite having a thickness of less than or equal to about 1 μm, and at least one metallic matrix of a phase mixture comprising at least one of martensite and bainite, residual austenite, and less than about 20% finely laminated pearlite with a lamella distance of less than or equal to about 1 μm;
• and
• the at least one martensite hardening zone comprising a phase mixture of at least one of martensite and bainite, partially dissolved pearlite, and residual austenite.