| In recent years, with the development of directional drilling technology in the oiland gas exploration industry. The exploration drilling tools, with a higher wear resis-tance, better corrosion resistance and non-magnetic properties, was more and moreneeded. Because of the wear and tear, the property of non-magnetic drill collar used indirectional well could be affected seriously. If the worn parts could not be repairedtimely, and the expensive drill collar will be discard as useless. Therefore, it couldcause a great materials waste. Laser cladding WC-FeNiCr non-magnetic hardalloy could strengthen and repair above componens perfectly, and then prolong itsserving life. In this work, the influencing factors on the magnetic properties of laserclad WC-FeNiCr composite coatings were studied in detail.Firstly, by changing the laser power and scanning speed, WC-FeNiCr compos-ite coatings were prepared on the surface of N1310non-magnetic steel by laser clad-ding method with a Trumpf6000W CO2laser. The magnetic properties of the clad-ding layer was analyzed with a Lake Shore7410type vibrating sample magnetometer,and the morphology of laser cladding layer was characterized with scanning electronmicroscopy (SEM). From the result, it could be learned that with the increase of laserpower, the thickness of the coating and the number of pores and cracks increased, andthe relative magnetic permeability also increased. When a power of1800W laser wasapplied, a good quality of cladding layer was fabricated, which has a moderate thick-ness and lower relative permeability. With the scanning speed increasing, the thick-ness of cladding layer decreased, and the number of pore and crack was also de-creased, however the relative magnetic permeability change little. When the scanningspeed keeps at240mm/min, the performance of cladding layer is better, therefore, theoptimized laser power and scanning speed in this work is1800W and240mm/minrespectively.Then, WC-FeNiCr hard alloy with different fractions of Ti、Mo、Mn additionswere prepared on the surface of N1310non-magnetic steel at the optimal laser clad-ding process. The magnetic properties of cladding layer were analyzed by Lake Shore7410type vibrating sample magnetometer. The morphology, composition and phaseanalysis of the coatings were carried out by SEM and TEM, EDS and XRD respec-tively. From the test result, it can be seen that the relative magnetic permeability of the coating decreases firstly and then increases with the increases of Ti addition,the minimum relative magnetic permeability is1.006at a Ti addition of2.5%. How-ever, with the increasing of Mo addition, the relative magnetic permeability increasesfirstly and then decreases, which is contrary to that of Ti addition, and a maximumrelative magnetic permeability of1.045is obtained when the Mo content is4.0%.With the increasing of Mn addition the relative magnetic permeability of lasercladding layer decreases.Lastly, the wear resistance, corrosion resistance and hardness of the laser clad-ding layer were tested by MMG-10Friction and Wear Tester, YW/R-150salt spraytest chamber and FM-300digital micro hardness tester respectively. The results showthat, the wear resistance of laser cladding WC-FeNiCr is far superior to the Ni-basedalloys. With the increasing of Ti addition, the wear loss of laser cladding WC-FeNiCrcomposite coatings increase, however, it is no effect of that with the addition of Mo inthe sample. The hardness of the cladding layer changed in a wide range because of thehardness of WC hard phase up to HV1500~2500while the Fe-based alloy matrix isabout only HV500~1000. When the Ti addition in the sample is greater than2.5%,the salt spray corrosion resistance is good, which could be equated to316stainlesssteel. However, when the Ti addition is less than2.5%or with the addition of Mo inthe sample, the salt spray corrosion resistance of which is bad. |
PDF Full Text Request