Zirconia Tungsten Disulfide Composite Self-lubricating Ceramics

With the development of science and technology, the research trend of self-lubricating technology is that solid lubricating materials without environmental pollution, long wear-resistant life, low friction and self-repairing are more and more widely used in high-tech fields such as electronics, biology, communications, aerospace and aviation. Future research mainly focuses on the research of new solid self-lubricating materials, new self-lubricating methods, new material structure design and other aspects.

The researchers used tungsten disulfide as lubricating phase to prepare high purity, high strength and high toughness zirconia-tungsten disulfide composite self-lubricating ceramics. The synthesis process includes:

(1)Select yttrium-stabilized zirconia powder with 3% molar percentage of yttrium oxide, and stabilize zirconia powder by weight ratio: tungsten disulfide powder = 9:1, weigh nano-sized yttrium-stabilized zirconia powder and tungsten disulfide powder The primary particle size of the yttrium-stabilized zirconia powder is 40 nm, the primary particle size of the tungsten disulfide powder is 50 nm, the purity of the yttrium-stabilized zirconia powder is 99.99%, and the purity of the tungsten disulfide powder is 99.99%. The nanopowder was placed in a ball mill jar and subjected to high energy ball milling for 8 hours using a high energy ball mill.

(2)Put polyvinyl alcohol, polyethylene glycol and deionized water into the ball milled mixed powder in step (1) and continue ball milling for 8 hours to obtain the mixed powder slurry.

(3)Mixing powder slurry in step (2) is added into a centrifugal spray granulator for granulation to become D50=57 micron granulation powder.

(4)The granulating powder obtained in step (3) was put into polyurethane cold isostatic pressing rubber sleeve for cold isostatic pressing treatment. The treatment pressure was 380 MPa and the holding time was 12 minutes.

(5)The cold isostatic pressing blank obtained in step (4) is put into the ladle sleeve, and the hot isostatic pressing sleeve is made by argon arc welding.

(6)Degreasing and degassing were carried out on the thermo-isostatic pressure envelope obtained in step (5). In the first stage, the degassing treatment parameters were 260 degrees, the treatment time was 12 hours, the pressure in the envelope was kept at 1.0*10-2~5.0*10-2 Pa, and in the second stage, the degreasing treatment parameters were 580 degrees, the treatment time was 18 hours, and the degassing was maintained in the envelope. The pressure is 1.0 *10-2~5.0 *10-2 Pa. The third stage of degassing treatment parameters are 260 degrees, the treatment time is 18 hours, and the degassing pressure is 1.0 *10-3~5.0 *10-3 PA.

(7)The degassed envelope obtained in step (6) is sintered by hot isostatic pressing in a hot isostatic press. The sintering pressure is 150 MPa, the sintering temperature is 1150 ℃, and the sintering time is 5 hours.

(8)The high purity, high strength and toughness zirconia-tungsten disulfide composite self-lubricating ceramics were obtained by taking out the ceramic ingot sintered by hot isostatic pressing and removing the envelope.

(9)The relative density, purity, friction coefficient, grain size, bending strength and hardness of ZrO₂-WS₂ self-lubricating ceramics are 99.6%, 99.9691%, 0.08, 4.7 micron, 1212 MPa and HV1608 respectively.

Nano scale yttria stabilized zirconia powder and nano scale two tungsten sulfide powder were used to mix and mechanically alloying the powders by high-energy ball milling. Then, granulation was made by centrifugal spray granulation and pressed by cold isostatic pressing, and finally by hot isostatic pressing sintering, stable quality and fine grain size could be obtained. Zirconia tungsten disulfide composite self-lubricating ceramics.

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