CN-121289470-B - Gradient nanocrystalline self-lubricating hard alloy and preparation method thereof

CN121289470BCN 121289470 BCN121289470 BCN 121289470BCN-121289470-B

Abstract

A preparation method of gradient nanocrystalline self-lubricating hard alloy for high-frequency servo transmission belongs to the field of metal powder processing, and specifically comprises the steps of respectively carrying out surface layer, transition layer and core batching ball milling to obtain surface layer powder, sequentially feeding, pressing and presintering the transition layer powder and the surface layer powder according to the sequence of the core powder, the transition layer powder and the surface layer powder, and then carrying out sintering treatment and surface layer regulation. According to the invention, the hard alloy is prepared into the gradient structure of the surface layer, the transition layer and the core part through different metal powder ingredients, the WC grain size gradient change from the surface layer to the core part is realized, the gradient change is also formed in the hard alloy through the binding phase content, and the partition change shape three-dimensional gradient transition of the functional components is realized, so that the high-hardness and internal high-toughness core structure is formed, meanwhile, the concentration of interlayer stress is avoided, the core part strong hardness is stabilized, and the alloy is suitable for the fatigue resistance requirement of high-frequency reciprocating motion.

Inventors

WU XIANG
LIAO TIANXING
LEI YU
DENG YING
GUO CHAOZHONG
GU JINBAO
HE YANG
XIONG WAN
SHEN KUN
He Miaojin
WANG TIANGANG

Assignees

自贡硬质合金有限责任公司
重庆文理学院

Dates

Publication Date: 20260512
Application Date: 20251128

Claims (7)

1. A preparation method of gradient nanocrystalline self-lubricating hard alloy for high-frequency servo transmission is characterized in that surface layer powder, transition layer powder and core powder are obtained by ball milling of ingredients of a surface layer, the transition layer powder and the core powder are sequentially fed, pressed and presintered according to the sequence of the core powder, the transition layer powder and the surface layer powder, sintering treatment and surface layer regulation are carried out, the surface layer powder is prepared from 88-90 wt% of WC, 4-8 wt% of Co, 1.2-1.8 wt% of graphite, 0.3-0.6 wt% of Cr 3 C 2 , 0.5-0.7 wt% of h-BN, 0.4-0.6 wt% of VC, 0.5wt% of TaC and 1-2 wt% of TiC according to the mass percentage, the transition layer powder is prepared from 84-86 wt% of WC, 10-12 wt% of Co, 2wt% of NbC 1.8-12 wt% of Cr 3 C 2 , the core powder is prepared from 84-86 wt% of WC, 10-86 wt% of Co 2wt% of Ni 2wt% of Cu, and 5-5.5 wt% of Cu powder, and the surface layer powder is prepared by mixing under the conditions of pressure of mixed powder and the conditions of the surface layer powder is carried out under the conditions of pressure of 0-3-4 MPa of mixed powder of the surface layer powder and the mixture of the surface layer powder is prepared by ball milling of the alloy powder is carried out under conditions of 0-3-4 MPa and the conditions of the surface layer powder is subjected to liquid phase powder is mixed with the conditions.
2. The method for preparing the gradient nanocrystalline self-lubricating hard alloy for high-frequency servo transmission according to claim 1, wherein the surface layer batching ball milling is carried out by taking absolute ethyl alcohol as a medium, adopting ZrO 2 balls for ball milling, wherein the ball material ratio is 12-15:1, the ball milling rotating speed is 300-350 rpm, the ball milling time is 12-18 h, and after ball milling, vacuum drying and sieving with a 200-mesh sieve are carried out, so that surface layer powder is obtained.
3. The method for preparing the gradient nanocrystalline self-lubricating hard alloy for high-frequency servo transmission according to claim 2, wherein the proportioning ball milling of the transition layer is carried out by taking kerosene as a medium, ball milling with WC-Co balls, the ball-material ratio is 10-12:1, the ball milling rotating speed is 250-300 rpm, the ball milling time is 6-10 h, and the mixture is dried and then passes through a 200-mesh sieve to obtain the transition layer powder.
4. The method for preparing the gradient nanocrystalline self-lubricating hard alloy for high-frequency servo transmission according to claim 3, wherein the core material is ball-milled by taking kerosene as a medium, ball-milling with WC-Co balls, the ball-material ratio is 8-10:1, the ball-milling rotation speed is 200-250 rpm, the ball-milling time is 6-10 h, and the core powder is obtained by sieving with a 200-mesh sieve after drying.
5. The method for preparing the gradient nanocrystalline self-lubricating hard alloy for high-frequency servo transmission of claim 4, wherein the pressing presintering molding is to fill powder after ball milling of each layer into a mold according to the sequence of a core part, a transition layer and a surface layer, perform the pre-molding under 160-280 MPa pressure, and then keep the temperature at 700-900 ℃ for 30-90 min.
6. The method for preparing the gradient nanocrystalline self-lubricating hard alloy for high-frequency servo transmission of claim 5, wherein the sintering treatment is two-step sintering, specifically, heat preservation is carried out for 20-60 min at 1350-1450 ℃, and then the temperature is reduced to 1250-1350 ℃ and heat preservation is continued for 30-90 min.
7. The preparation method of the gradient nanocrystalline self-lubricating hard alloy is characterized by comprising the following steps of: s1, proportioning and ball milling 88-90 Wt% of WC, 4-8 wt% of Co, 1.2-1.8 wt% of graphite, 0.3-0.6 wt% of Cr 3 C 2 , 0.5-0.7 wt% of h-BN, 0.4-0.6 wt% of VC, 0.5wt% of TaC and 1-2 wt% of TiC, taking absolute ethyl alcohol as a medium, performing ball milling by adopting ZrO 2 balls, wherein the ball material ratio is 12-15:1, the ball milling rotating speed is 300-350 rpm, the ball milling time is 12-18 h, and after the ball milling is finished, performing vacuum drying and sieving by a 200-mesh sieve to obtain surface powder; Preparing materials of a transition layer, namely, 84-86 wt% of WC, 10-12 wt% of Co, 2wt% of Ni, 1-1.5 wt% of NbC and 0.8-1.2 wt% of Cr 3 C 2 , performing ball milling by using a WC-Co ball as a medium, wherein the ball-material ratio is 10-12:1, the ball milling rotating speed is 250-300 rpm, the ball milling time is 6-10 h, and after ball milling is finished, performing vacuum drying and sieving the transition layer powder by a 200-mesh sieve; Preparing materials in a core, namely, 84-86 wt% of WC, 10-14 wt% of Co, 2wt% of Ni and 1.5-2.5 wt% of NbC, performing ball milling by using kerosene as a medium, performing ball milling by using WC-Co balls, wherein the ball-material ratio is 8-10:1, the ball milling rotating speed is 200-250 rpm, the ball milling time is 6-10 hours, and performing vacuum drying and sieving by using a 200-mesh sieve after ball milling is finished to obtain core powder; S2, layered filling preforming Filling each layer of ball mill powder into a mold according to the sequence of the core powder, the transition layer powder and the surface layer powder, preforming under 160-280 MPa pressure, and then preserving heat at 700-900 ℃ for 30-90 min; S3, sintering treatment Firstly preserving heat for 20-60 min at 1350-1450 ℃, and then cooling to 1250-1350 ℃ and continuously preserving heat for 30-90 min; S4, surface layer regulation and control Burying the alloy by adopting mixed ball milling of Cu powder, zn powder and Cr powder, introducing NH 3 ,NH 3 at 560-620 ℃ with a flow of 5-7L/min, applying 0.1-0.3 MPa pressure, preserving heat for 3-4 h, wherein Zn in the composite powder is 5-6wt%, cr powder is 1-2wt% and the balance Cu powder, ball milling is carried out by taking absolute ethyl alcohol as a medium and WC balls with a ball material ratio of 3-4:1, a ball milling rotating speed of 200-250 rpm, a ball milling time of 1-1.5 h, and drying after ball milling is finished to obtain the composite powder.

Description

Gradient nanocrystalline self-lubricating hard alloy and preparation method thereof Technical Field The invention relates to the technical field of metal powder processing, in particular to a gradient nanocrystalline self-lubricating hard alloy for high-frequency servo transmission and a preparation method thereof. Background Tungsten carbide (WC) has excellent properties of Mohs hardness of 8.5-9.0 and melting point 2870 ℃ by virtue of a hexagonal structure formed by a W-C covalent bond, and becomes a core material in the fields of machine manufacturing, mining, aerospace and the like after conforming to Co and the like. At present, a diversified preparation system is formed at home and abroad to improve the performance. However, the traditional tungsten carbide hard alloy faces serious performance paradox that the toughness is reduced by increasing the hardness (increasing the WC content/refining grains), the hardness is sacrificed by increasing the toughness (increasing the Co content of a binding phase), and the application of the hard alloy under specific working conditions is limited. Based on the above, the hard alloy with a multilayer structure appears in the prior art, and the ideal combination of the properties of external hardness and internal toughness is realized through the high hardness and wear resistance of the external layer and the high toughness and impact resistance of the internal layer. However, in the process of preparing the multilayer structure, because of large difference of thermal expansion coefficients of WC and Co, extremely large residual stress is generated in the cooling process, so that interfacial peeling is caused, brittle eta phase is easily generated in high-temperature sintering, and the interfacial strength is reduced. To solve the above problems, a transition layer may be added to alleviate the above problems, but it is difficult to tune the grain change of WC during the preparation process, and the uniformity of grain growth is not controllable, resulting in unstable performance. Disclosure of Invention The invention aims to provide a gradient nanocrystalline self-lubricating hard alloy for high-frequency servo transmission. The invention further aims at providing a preparation method of the gradient nanocrystalline self-lubricating hard alloy for high-frequency servo transmission. The invention aims at realizing the following technical scheme: The gradient nanocrystalline self-lubricating hard alloy is characterized by comprising a surface layer, a transition layer and a core part, wherein the surface layer is prepared from 88-90wt% of WC, 4-8wt% of Co, 1.2-1.8wt% of pore-forming agent (graphite), 0.3-0.6wt% of Cr 3C2, 0.5-0.7wt% of h-BN, 0.4-0.6wt% of VC, 0.5wt% of TaC and 1-2wt% of TiC by mass percent, the transition layer is prepared from 84-16wt% of WC, 10-12wt% of Co, 1-1.5wt% of NbC and 0.8-1.2wt% of Cr 3C2, and the core part is prepared from 84-16wt% of WC, 10-14wt% of Co, 2wt% of Ni and 1.5-2.5wt% of NbC by mass percent. Further, the thickness of the surface layer of the gradient nanocrystalline self-lubricating hard alloy is 10-50 mu m, the size of WC crystal grains is 50-200 nm, the thickness of the transition layer is 150-300 mu m, the size of WC crystal grains is 0.5-0.5 mu m, and the size of core WC crystal grains is 0.3-0.8 mu m. A preparation method of a gradient nanocrystalline self-lubricating hard alloy for high-frequency servo transmission is characterized in that surface layer powder is obtained by respectively carrying out surface layer, transition layer and core batching ball milling, the transition layer powder and the core powder are sequentially fed, pressed and presintered according to the sequence of the core powder, the transition layer powder and the surface layer powder, and then sintering treatment and surface layer regulation are carried out. Further, according to mass percentage, the surface layer powder is prepared from 88-90 wt% of WC, 4-8 wt% of Co, 1.2-1.8 wt% of pore-forming agent (graphite), 0.3-0.6 wt% of Cr 3C2, 0.5-0.7 wt% of h-BN, 0.4-0.6 wt% of VC, 0.5wt% of TaC and 1-2 wt% of TiC, the transition layer powder is prepared from 84-86 wt% of WC, 10-12 wt% of Co, 2wt% of Ni, 1-1.5 wt% of NbC, 0.8-1.2 wt% of Cr 3C2, and the core powder is prepared from 84-86 wt% of WC, 10-14 wt% of Co, 2wt% of Ni and 1.5-2.5 wt% of NbC. Further, the surface layer batching ball milling is carried out by adopting absolute ethyl alcohol medium, zrO 2 balls are adopted for ball milling, the ball-material ratio is 12-15:1, the ball milling rotating speed is 300-350 rpm, the ball milling time is 12-18 h, and after the ball milling is finished, vacuum drying and sieving with a 200-mesh sieve are carried out. Further, the transition layer batching ball milling is carried out by taking kerosene as a medium and WC-Co balls, wherein the ball-material ratio is 10-12:1, the ball milling rotating speed is 250-300 rpm, the ball milling time is 6-10 h, and t