Fatigue Strength of Hard Coating in Different Stress States

By means of bend fatigue tests and push-pull fatigue tests,the fatigue strength of Ni base-WC composite coating specimens was compared in different stress states.Under bend-rotation fatigue,fatigue strength of coating specimens was 80 MPa more than that of uncoated specimens in the same fatigue life.Under push-pull fatigue,in N<3×104,fatigue strength of coating specimens was higher than that of uncoated specimens,but in N>3×104,it was contrary.The bend-rotation fatigue strength of coatings and uncoated specimens was 75MPa and 25 MPa,respectively,more than the push-pull fatigue strength.