航空用PH13-8Mo沉淀硬化不锈钢试样经直接淬硬法热处理后采用常规的不锈钢浸蚀剂不能有效显示晶界。分别采用氧化法与直接淬硬法对试样热处理，其中直接淬硬法热处理后，采用多种浸蚀剂进行浸蚀，然后进行晶粒度评定。结果表明：采用氧化法可得到更加真实、完整、清晰的晶粒形貌，是一种有效、方便、环保的晶粒度评定方法，可用于该钢晶粒度检验；直接淬硬法采用92 mL HCl+5 mL H₂SO₄+3 mL HNO₃浸蚀剂室温浸蚀1 min或1 g KMnO₄+10 mL H₂SO₄+100 mL H₂O浸蚀剂热浸蚀2 min，晶界显示清晰。

It is invalid that the grain boundary shown from the specimen of PH13-8Mo precipitation-hardening stainless steel for aviation after heat treatment of direct hardening and etched by normal stainless steel etching solution. Comparison oxidation method with direct hardening method by various corrosion, the results show that oxidation method lead to the real, integrity, clear grain morphology. It is a valid, convenient and environmental method for grain size evaluation of steel PH13-8Mo; 92 mL HCl+5 mL H₂SO₄+3 mL HNO₃ immersion at room for 1 min or 1 g KMnO₄+10 mL H₂SO₄+100 mL H₂O thermal etching for 2 min by direct hardening method can produce clear grain boundaries.