齿轮渗氮用材主要有42CrMo、25Cr2MoV、34CrNi3Mo、40CrNiMoGrMo钢等,其中42CrMo钢的氮化层深显示最为困难。硝酸酒精溶液对这种材料的层深显示不起作用;用硫酸铜盐酸水溶液或氯化铜盐酸水溶液腐蚀,则往往侵蚀过剧,出现枝晶偏析,层深界限极不明显。如果把这两种溶液稀释后侵蚀,则试样上铜沉淀很厉害,也显示不出层深。因此需寻找适于显示42CrMo钢渗氮层的侵蚀剂。众所周知,大多数侵蚀剂都是在实验的基础上发展起来的。近年来,彩色金相在我国得到了迅速发展,一些化学着色试剂如焦亚硫酸盐-硫代硫酸盐试剂、硒酸等试剂也得到了应用,这些试剂中有一些可使整个氮化层着色,从而可对氮化层进行测定,如硒酸试剂。还有一些试剂可使铁素体、奥氏体着色,而碳化物、氮化物则呈白色。据有关资料介绍,这些试剂均用于 Gear nitriding materials are 42CrMo, 25Cr2MoV, 34CrNi3Mo, 40CrNiMoGrMo steel, which 42CrMo steel nitride layer shows the most difficult. Nitric alcohol solution on the depth of this material shows no effect; with copper sulfate aqueous solution of hydrochloric acid or copper chloride aqueous solution of corrosion, the erosion is often over drama, there dendrite segregation, the depth of the boundaries is very obvious. If these two solutions are diluted and eroded, the copper deposits on the sample are very good, and no depth is shown. Therefore, we must find suitable for showing 42CrMo steel nitriding layer of etchant. As we all know, most etchants are developed on the basis of experiments. In recent years, the color metallography has been rapidly developed in our country, some chemical coloring reagents such as metabisulfite - thiosulfate reagent, selenium and other reagents have also been applied, some of these reagents can make the entire nitride layer coloring , So that the nitride layer can be measured, such as selenium reagent. There are some reagents can make ferrite, austenitic coloring, while the carbide, nitride is white. According to the information, these reagents are used