| By using scanning electron microscopy, X-ray diffractometry, metallographic analysis, hardness testing and dynamic polarization testing, The varied rules of the surface structure, morphologies and properties of 4Crl4Ni14W2Mo valve steel after pre-treatment, before and after the ion nitriding had been studied. The results showed that a fine oxidation (phosphate) film was formed on surface layer. Compared with the original sample, the hardness and corrosion resistance of the sample were changed little by phosphating pre-treatment. With the increasing of oxidation temperature, the sample hardness is increased firstly, then declined, and corrosion resistance are always reduced, as the rise of oxidation temperature corrosion resistance is firstly reduced and then increased, at 450℃, the hardness is the highest and corrosion resistance is the worst.After ion nitriding, the hardness of the samples is significantly improved. Compared with the primitive sample had been nitrided, the hardness of nitrided sample has been little effected after phosphating pretreatment. The hardness of nitrided sample was improved obviously by oxidation pretreatment in different temperatures. With the increasing of pre-oxidation temperature, the hardness of the sample firstly arises and then drops, at 450℃, the value of hardness is maximum. The hardness of the samples was improved most obviously in titanium-atmosphere ion nitriding.After ion nitriding, the corrosion resistance of the nitrided sample was decreased obviously. Compared with the primitive sample had been nitrided, after pre-treatment, the corrosion resistance of the nitrided sample had increased. The corrosion resistance of nitrided sample was increased little after pre-phosphated; the corrosion resistance of nitrided sample was increased obviously after it had been pre-oxidated at 450℃; The corrosion resistance of the nitrided specimen was the best in an atmosphere of titanium, which was the same as that of the primitive sample.
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