渗碳处理对95W-3.4Ni-1.6Fe高比重合金显微组织和接触疲劳性能的影响（英文）

采用固体渗碳法对95W-3.4Ni-1.6Fe高比重合金进行了渗碳处理,并在球棒试验机上研究了渗碳处理对钨合金接触疲劳性能的影响。利用SEM、EDS、XRD、表面形貌仪等手段对渗碳钨合金的显微组织和疲劳损伤形貌等进行了表征。结果表明,渗碳处理后钨合金表面由较薄的多孔碳化钨层和被碳化钨包裹的改性钨颗粒层组成。渗碳处理不仅降低了钨合金的接触疲劳性能而且加剧了对偶件钢球的磨损。钨合金的损坏机制为剥落和层状分离,次表层主裂纹易在最大剪切应力处萌生并沿着钨–钨界面扩展。渗碳钨合金的损坏是由碳化钨颗粒的剥落造成,同时剥落后的碳化钨颗粒在接触界面间充当第三体,加剧了渗碳钨合金的表面磨损。

Microstructure and mechanical properties of TiAl/Ni-based superalloy joints vacuum brazed with Ti-Zr-Fe-Cu-Ni-Co-Mo filler metal

For the purpose of elevated temperature service and weight reduction in aerospace vehicle applications,a novel Ti-Zr-Fe-Cu-Ni-Co-Mo filler metal was employed to join TiAl to Ni-based superalloy(GH536).The effects of brazing temperature on interfacial microstructure and chemical composition of the joints were analyzed.The representative joint microstructure from TiAl substrate to GH536 substrate was primarily composed of four characteristic layers in order:B_(2);Al_(3)NiTi_(2);AlNi_(2)Ti containing Cr-rich(Cr,Ni,Fe)_(ss)(subscript ss represents solid solution),Ni-rich(Ni,Cr,Fe)_(ss) and TiNi3;Cr-rich(Cr,Ni,Fe)_(ss)containing AlNi_(2)Ti,Ni-rich(Ni,Cr,Fe)_(ss) and TiNi3.Layer IV has the majority of the brazing seam,while LayerⅡwas the thinnest.And the thickness of LayerⅡwas not affected by brazing temperature.With the increase in brazing temperature in the range of 1110-1170℃,both the shear strength and the thickness of brazing seam firstly increased and then decreased.The joint performance was jointly controlled by the thickness of brazing seam,the amounts of microcracks and intermetallic compounds formed in brazing seam.The maximum shear strength of 183 MPa at room temperature was obtained together with a peak thickness when the joint was brazed at 1150℃for 10 min and the shear fracture mainly occurred in the thinnest LayerⅡAl_(3)NiTi_(2).

Wear Behavior and Mechanism of a Sliding Pair of 0.1C-3Cr-2W-V Nitrided Steel Rubbing against an Aluminum Bronze Alloy

Wear behavior and mechanism of plasma nitrided steel oscillating against a heat-treated and an untreated aluminum bronze alloy were investigated using an Optimol SRV tribometer.The influence of heat treatment on the mechanical properties of the alloy was evaluated.Furthermore,the wear debris was also examined to understand the wear mechanisms.The results show that a 220-230μm nitrided layer,which was harder than the substrate,was obtained on the steel surface.The tensile strength and hardness of the alloy are found to be significantly improved by the heat treatment associated with low impact toughness.The heat treatment of the alloy did not obviously decrease the friction coefficient of the nitrided steel-bronze couple.However,the wear loss of the nitrided steel increased when it mated with the treated bronze by a severe three-body abrasion.The nitrided steel was mainly damaged by fatigue spalling.Under plane contact conditions,the wear debris was mainly generated from the bronze part and can escape from the interface before being oxidized,leading to the phase structure of all the debris being copper rather than copper oxides.

Microstructure and tribological properties of carburized 95W–3.5Ni–1.0Fe–0.5Co heavy alloy

Tungsten heavy alloys(WHAs) produced by powder technology are widely used for the mechanical manufacturing, electronic and defense components, etc.Tribological properties of these alloys need to be improved to meet the severe service conditions demanded. Carburization is a promising way to resolve this problem. In this work, microstructure and tribological properties of the carburized 95W–3.5Ni–1.0Fe–0.5Co heavy alloy were investigated in comparison with those of the untreated alloy. Results show that the carburized layer consists of a porous, outer WC layer and a modified W grain layer surrounded by Fe_6W_6C and Co_6W_6C at 970℃, regardless of the carburizing time. The depth of the carburized layer linearly increases in a relatively short time and slightly increases during the subsequent period. Surface roughness increases with carburizing time. Carburization can stabilize friction coefficient and effectively improve the wear resistance of the tungsten heavy alloy due to its significantly increased hardness and non-deformability, but the porous structure in the WC layer has a negative influence on its wear resistance. The carburized layer is damaged in the porous WC layer in the form of the spalling of WC particles where there are some microcracks and micropores, accompanied with peeling due to the solid tribofilm being pushed away.