Microstructure and Sliding Wear Performance of Cr 7 C 3 -(Ni,Cr) 3 (Al,Cr) Coating Deposited from Cr 7 C 3 In Situ Forme
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Microstructure and Sliding Wear Performance of Cr7C3(Ni,Cr)3(Al,Cr) Coating Deposited from Cr7C3 In Situ Formed Atomized Powder Hong-Bin Zhu1 • Jie Shen1 • Feng Gao1 • Yueguang Yu1 • Changhai Li1
Submitted: 30 May 2016 / in revised form: 10 October 2016 ASM International 2016
Abstract This work is aimed at developing a new type of Cr7C3-(Ni,Cr)3(Al,Cr) coating for parts used in heavy-duty diesel engines. The feedstock, in which the stripe-shaped Cr7C3 was in situ formed, was firstly prepared by vacuum melting and gas atomization and then subjected by highvelocity oxy-fuel spraying to form the coatings. The carbon content, microstructure and phase constitution of the powders, as well as the sprayed coatings, were analyzed by chemical analysis, SEM and XRD. The hardness and sliding wear performance of the sprayed coatings were also tested and compared to a commercial Cr3C2-NiCr coating used on piston rings. The results showed that the content of carbon in feedstock was almost the same as designed, and that the volume content of in situ formed Cr7C3 was increased with carbon and chromium added. The major phases of the powders and sprayed coatings are Cr7C3 and Cr-alloyed Ni3Al. Only a small amount of carbon lost during the spraying process. As Cr7C3 content increased in the coatings, the microhardness at room temperature was firstly increased to about 1000Hv0.3. The microhardness of the coatings stayed almost constant, while the testing temperature was raised up to 700 C for 0.5 h, which illustrates the potential application of the investigated
This article is an invited paper selected from presentations at the 2016 International Thermal Spray Conference, held May 10–12, 2016, in Shanghai, P.R. China, and has been expanded from the original presentation. & Hong-Bin Zhu [email protected] 1
Beijing General Research Institute of Mining and Metallurgy, Beijing Engineering Technology Research Center of Surface Strengthening and Repairing of Industry Parts, Beijing 102216, China
coatings under high temperature conditions. The coatings containing 70 and 77 vol.% Cr7C3 showed the most promising wear resistance, lower friction coefficient and better tribological compatibility to gray cast iron counterpart than other tested Cr7C3-(Ni,Cr)3(Al,Cr) coatings and the reference Cr3C2-NiCr coating. Keywords Cr7C3-(Ni,Cr)3(Al,Cr) gas atomization HVOF wear resistance
Introduction Modern heavy-duty diesel engines work under a high pressure (180-195 bars) and temperature (around 600 C in exhaust gases). In these conditions, the oil lubrication failed, and the parts in it would suffer severe wear (Ref 1). Thermal spraying is an effective surface modification technology to deposit wear-resistant coatings on the industrial parts. In the past twenty years, the conventional ceramic-metallic composited coatings, such as WC-Co and CrxCy-NiCr coatings, have been applied on the wear parts in the diesel engines (Ref 2-5). However, the WC-Co coating proved unsuitable for wear protection above 450 C (Ref 6). Although t
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