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在铁石墨为基的粉末冶金零件中,其显微组织除孔隙和自由石墨碳外,一般为珠光体、铁素体及渗碳体;或者为珠光体及铁素体;珠光体及渗碳体三种类型。平时对这些粉末冶金零件作金相检验时侵蚀剂一般都用碳酸酒精溶液侵蚀以显示组织。如只存在两种组织则较方便,即能判别,但若三种组织同时存在时,则铁素体和渗碳体两者之间往往很难区别。因此用硝酸酒精溶液侵蚀不能解决问题,虽有时也利用碱性苦味酸钠溶液加热侵蚀使试样中渗碳体变色发暗来帮助判别,但由于铁石墨粉末冶金试样中存存着黑色孔隙、自由石墨等,
In graphite-based powder metallurgy parts, the microstructure is generally pearlite, ferrite and cementite except for pores and free graphitic carbon, or pearlite and ferrite, pearlite and carburized Three types of body. Usually these metallurgical parts for metallurgical test etchants are generally eroded with carbonated alcohol solution to show the organization. If there are only two organizations is more convenient, that is, to determine, but if the three organizations exist at the same time, the ferrite and cementite are often difficult to distinguish between the two. Therefore, erosion with nitric acid solution can not solve the problem, although sometimes the use of alkaline solution of sodium picrate heat erosion so that the sample cementite discoloration to help determine the dark, but the graphite iron powder metallurgy samples stored in black pores , Free graphite, etc.,