Corrosion resistant device

1. A corrosion resistant device comprising:

a first member having a plated layer applied to a metal base material; and

a second member pressed against a portion of the first member on which the plated layer is applied, wherein

a stress caused in the first member by pressing the second member against the first member is defined as a tensile stress,

a probability of breakage of the plated layer caused by the tensile stress is defined as a breakage probability,

a slope of a characteristic line, which represents a relationship between an elastic modulus of the plated layer and the breakage probability, is a ratio of an increase amount of the breakage probability to a decrease in the elastic modulus by a predetermined amount and is defined as a characteristic slope,

a change point that appears on the characteristic line, at which the elastic slope changes from a slope, which is less than a predetermined slope, to a predetermined slope or more as the elastic modulus gradually decreases, is defined as a characteristic change point,

the elastic modulus at the characteristic change point is defined as a characteristic change elastic modulus, and

the plated layer contains at least a chromium component and has the elastic modulus larger than the characteristic change elastic modulus.

2. The corrosion resistant device according to claim 1 , wherein

the characteristic change elastic modulus is set to 1.6×10 5 N/mm 2 or more based on the characteristic line when the tensile stress is 1100 MPa.

3. The corrosion resistant device according to claim 2 , wherein

a void ratio is defined as a ratio of voids, each of which is 0.001 μm 2 or larger, among voids appearing in an arbitrary cross section of the plated layer, and

the plated layer is formed to have the void ratio equal to or less than 0.5%.

4. The corrosion resistant device according to claim 1 , wherein

the characteristic change elastic modulus is set to 1.2×10 5 N/mm 2 or more based on the characteristic line when the tensile stress is 800 MPa.

5. The corrosion resistant device according to claim 4 , wherein

a void ratio is defined as a ratio of voids, each of which is 0.001 μm 2 or larger, among voids appearing in an arbitrary cross section of the plated layer, and

the plated layer is formed to have the void ratio equal to or less than 1.0%.

6. The corrosion resistant device according to claim 1 , wherein

the elastic modulus is larger than the characteristic change elastic modulus which is specified by a liner function in which the tensile stress is a variable, and

the linear function, which specifies the characteristic changer elastic modulus, has an inclination, which is 400/3, and an intercept, which is 40000/3.

7. The corrosion resistant device according to claim 1 , wherein

a void ratio is defined as a ratio of voids, each of which is 0.001 μm 2 or larger, among voids appearing in an arbitrary cross section of the plated layer,

the void ratio is less than an upper limit value which is specified by a liner function in which the tensile stress is a variable, and

the linear function, which specifies the upper limit value, has an inclination, which is −1/600, and an intercept, which is 7/3.

8. The corrosion resistant device according to claim 1 , wherein

the corrosion resistant device is configured to be mounted on a combustion system having an internal combustion engine, wherein

the first member is configured to be mounted on the combustion system to be exposed to an exhaust gas of the internal combustion engine.

9. The corrosion resistant device according to claim 8 , wherein

the first member and the second member are configured to be provided in a fuel injection valve for injecting fuel into a combustion chamber of the internal combustion engine, and

the tensile stress as a condition for specifying the characteristic line is a magnitude generated in a state in which the fuel injection valve is mounted on the combustion system.

10. The corrosion resistant device according to claim 9 , wherein

the first member has an injection hole for injecting fuel into the combustion chamber, and

the plated layer is applied to an area spreading from one portion of an outer surface of the first member where the injection hole resides to another portion of the outer surface pressed against the second member.

11. The corrosion resistant device according to claim 1 , wherein

a film thickness of the plated layer is 0.1 μm or more and less than 10 μm.

12. The corrosion resistant device according to claim 1 , wherein

the second member includes a second plated layer that is pressed against the plated layer and a second base material made of a metal to which the second plated layer is applied,

a stress caused in the second member by being pressed against the first member is defined as a second tensile stress,

a probability of breakage occurring in the second plated layer by the second tensile stress is defined as a second breakage probability,

a second characteristic line represents a relationship between a second elastic modulus, which is an elastic modulus of the second plated layer, and the second breakage probability, which is a ratio of an increase amount in the second breakage probability to a decrease in the second elastic modulus by a predetermined amount,

a slope of the second characteristic line is defined as a second characteristic slope,

a change point appearing in the second characteristic line, at which the second characteristic slope changes from a slope less than a predetermined slope to the predetermined slope or more as the second elastic modulus gradually decreases, is defined as a second characteristic change point,

the second elastic module at the second characteristic change point is defined as a second characteristic change modulus, and

the second plated layer has the second elastic modulus larger than the second characteristic change elastic modulus.