Cylinder liner and method construction thereof

1. A cast iron cylinder liner for receipt in an internal combustion engine cylinder block having a water cooling jacket surrounding a portion of the cylinder liner to facilitate regulating the temperature of the cylinder liner, said cylinder liner, comprising:

a cylinder liner wall having an inner surface providing a cylinder bore extending along a central axis for reciprocation of a piston against an axial portion of said inner surface and an outer surface opposite said axial portion, said outer surface having a hardened outer layer of purely martensitic microstructure for direct exposure to the water cooling jacket, wherein said inner surface and said outer surface define a wall thickness of said cylinder liner wall, said hardened outer layer having a hardened depth equal to 10 percent or less of said wall thickness, said hardened depth being greater than zero.

2. The cast iron cylinder liner of claim 1 wherein said hardened depth is between about 0.5 mm and 1.5 mm.

3. The cast iron cylinder liner of claim 1 wherein said hardened outer layer has a hardness between about 42-55 Rc.

4. A method of constructing a cast iron cylinder liner for an internal combustion engine, comprising:

casting an iron cylinder liner body having a cylinder wall with a cylinder bore and an outer surface;

machining an inner surface of the cylinder bore;

machining at least a portion of said outer surface opposite said inner surface; and

heat treating said machined portion of said outer surface to provide a purely martensitic hardened layer having a depth equaling 10 percent or less of a thickness of said cylinder wall, said depth being greater than zero.

5. The method of claim 4 wherein said heat treating step includes tempering said hardened layer.

6. The method of claim 5 further including tempering said hardened layer to a hardness between about 42-55 Rc.

7. The method of claim 4 further including performing said heat treating step using an induction heating process.

8. The method of claim 4 further including forming said hardened layer having a depth of between about 0.5 to 1.5 mm.