Study On Pack Boronizing Of Steel Cr12MoV

The pack boronizing of Crl2MoV steel is carried by orthogonal tests, and by use of agents made by myself. Microstructure observing and phase analysis of boronizing layer are finished through Olympus(BH-2) microscope, QUANTA-200 SEM, JSM-6700F SEM, HV-1000 microhardometer. The wear resistance are measured through M-200 wear tester and ML-100 abrasive wear tester at room temperature. Following heat treatment is done in SX2-12-10 box stove.Experimental results show that 950℃ ×7h is optimizing process parameters for general boronizing; and while 950℃×5h is optimizing process parameters for RE-boronizing, and an optimum value of the addition of RE element in the agent is 0.3%.Following heat treatment process is quenching at 970℃ and tempering at 200 ℃.Whether general boronizing or optimizing RE-boronizing microstructure of boronizing layer is same, boronizing layer all consists of boride layer and transition zone. Boride layer consists mainly of FeB, Fe₂B, (Fe, Cr)₂B, fine (Fe, Cr) ₃C, block(Cr, Fe)₇C₃and a little(Fe, Cr)₂₃C₆ phases. Transition zone consists mainly of beard (Fe, Cr )₂B, block(Cr, Fe)₇C₃, fine (Fe, Cr )₃C, island(Fe, Cr)₂₃C₆ phases and troostite. Both boride and carbonization can strengthen and thin the microstructure and improve greatly support of boride layer, this will benefit binding of the boronizing layer and matrix.Under the same boronizing process( 600℃ ×5h→950℃ ×5h), the depth of optimizing RE-boronizing layer is increased 1/5 in comparison with general boronizing. Otherwise, comparing optimizing RE-boronizing layer with general boronizing layer, the microstructure of boronizing case after optimizing RE-boronizing is more compact and there are fewer defects such as porosity and hole. Whether general boronizing or optimizing RE-boronizing, the difference of microhardness of boronizing layer is little. Microhardness of boronizing layer distributes gradationally, the hardest points appear in the second layer while not in the surface layer, but the microhardness curve of optimizing RE-boronizing layer is more low-grade, while that of general boronizing layer is high-grade. Comparison on the brittleness, the brittleness of optimizing boronizing layer is grade one, while that of general boronizing layer is grade three, the former is lower tow grades than the latter. Comparison on the wear resistance, the wear resistance of optimizing boronizing layer exceed that of general boronizing layer by fifteen times.Whether general boronizing or optimizing RE-boronizing, the boronizing temperature is all important influence factor. The more boronizing temperature raises,the more depth of boronizing layer increases, at the same time there are more porosities and holes in the boride layer.Whether general boronizing or optimizing RE-boronizing, the depth of boronizing layer increases as boronizing time lengthens. But for general boronizing, there is optimal holding time for five hours, while boronizing time passes beyond five hours, the depth of general boronizing layer increases slowly. For optimizing...