Study On Low-temperature Aluminizing On 304 Stainless Steel Assisted By Sand Blasting

304 stainless steel(06Cr19Ni10) is a Cr-Ni austenitic stainless steel which has excellent performance and be widely used in many places, but it will be damaged in work environment. There are many local corrosion phenomena such as pitting corrosion and stress corrosion cracking. Because it has a high concealment, easily cause serious engineering accident. Stainless steel surface aluminized technology is a mature and effective method to solve the above problems. But the traditional pack cementation aluminized technology that has high temperature and long heat resulting in energy consumption and low efficiency will influence on the performance of workpiece. The thesis analyze existing the theory of mechanical energy aided diffusing and creatively combine embedding sandblasting with pack cementation aluminizing for the first time to realize the low-temperature aluminizing. This method greatly simplifies the process and equipment which has the crucial practical significance and applied value.In the thesis, first type 304 stainless steel plates were treated by sand blasting, then pack cementation aluminizing and heat treating. It studies the best process parameters of low-temperature aluminizing, calculates the activation of aluminizing by using Arrhenius formula, and analyzes the microstructure and properties of aluminized layer. The results of study shows as follow:(1) The best process parameters of sand blasting: pressure is 0.5Mpa, the distance is 5cm, the time is 5 minutes, and abrasive particle size is 120 meshes. The sand blasting specimen shows a better stability when its surface obtains martensite transformation after heat treating at 400~600 ℃for 1~4hours; The aluminized agent composition: Zn:Al:NH4Cl=40:60:3, the Aluminized layer can reach 50μm thickness with pack cementation aluminizing which be treated at 530 for 3 h℃ ours, but the aluminized layer with original sample is only 10μm.(2) It be calculated that the activation of low-temperature aluminizing is 161.08KJ/mol by using Arrhenius formula. It compared with traditional pack cementation aluminizing’s 202.14KJ/mol that is clear decline.(3) The layer consists mainly FeAl2 phase, the result of energy spectrum analysis is Al:Fe≈2.2:1, it’s as same as x ray diffraction analysis.(4) In the surface layer from 30μm, the hardness of layer reaches 640HV0.2 which is more than 3 times as hardness as 304 stainless steel.(5) Aluminized steel has a good corrosion resistance. The corrosion weightlessness of aluminized stainless steel which dip in liquor of NaCl is only 1/17 of original sample’s; The result of electrochemical corrosion is E aluminized sample>E original sample, i aluminized sample<i original sample; The FeCl3 corrosion test at 35 for 24 hours, the corrosion rate of aluminized sample is 27.16g/(m℃2·h) which is half of the corrosion rate of original sample; The FeCl3 corrosion test at 50 ℃for 24 hours, the corrosion rate of aluminized sample is 70.83g/(m2·h) which less than half of original sample. With the temperature increase, the corrosion rate of aluminized sample increase slowly compared with original sample.(6) Oxidation resistance of aluminized sample is better than original sample obviously. After conventional thermal oxidation treatment at 850 for 24 hours and 36 hours, the oxidation weight ℃of original sample respectively are 4 and 10 times the weight of aluminized sample. After conventional thermal oxidation treatment at 850 for 36 hours, then the spi℃ nel phase will form on the surface of aluminized sample.(7) The friction coefficient of aluminized sample is lower than original sample’s. The aluminized layer has a good anti-friction effect. The aluminized layer significantly improve performance of the surface of tribology, the abrasion loss of aluminized sample for 45 minutes is 0.2 times as many as original sample for 30 minutes, the wear rate of aluminized sample for 45 minutes is 0.22 times as many as original sample for 30 minutes.