Investigation on diffusion bonding of functionally graded WC–Co/Ni composite and stainless steel

doi:10.1016/j.matdes.2012.11.006

Materials & Design (1980-2015)

Volume 46, April 2013, Pages 622-626

https://doi.org/10.1016/j.matdes.2012.11.006 Get rights and content

Abstract

A functionally graded WC–Co/Ni composite (FGWC) and 410 stainless steel (410ss) were successfully bonded by diffusion bonding. With the bonding temperature or holding time increasing, the tensile strength of the joints increased firstly and then decreased. The maximum tensile strength of the FGWC/410ss joints was 195 MPa bonded at 950 °C for 80 min. A diffusion layer was formed between the Ni layer and the 410ss as a result of the interdiffusion of Ni and Fe. The Ni layer could release the residual stresses of the FGWC/410ss joints. The fracture of the FGWC/410ss joints occurred in the Ni layer by the way of ductile fracture.

Highlights

► The FGWC and 410ss were successfully bonded by means of diffusion bonding. ► A diffusion layer was formed between the Ni layer and 410ss due to the interdiffusion of Ni and Fe. ► The maximum tensile strength of the FGWC/410ss joints was 195 MPa. ► The fracture of the FGWC/410ss joints occurred in the Ni layer.

Introduction

Cemented carbides (WC–Co) consist of a large amount of WC particles embedded in Co binder [1]. Due to their high hardness (especially in high temperature), strength, erosion resistance, wear resistance and low thermal expansion coefficient, cemented carbides are the most important materials for cutting, drilling and mining tools [2], [3]. In order to further expand their practical applications, cemented carbides are usually joined with steels by using Cu-based solders or Ag-based solders. Chen et al. [4] used Cu–Zn alloy electroplated Ni as interlayer to join cemented carbide with 3Cr13 stainless steel. Lee et al. [5] brazed WC–Co and carbon steel using multiple layers of Cu and Ni alloys as insert metal. Barrena et al. [6] designed a Cu/Ni electroplated interlayer to join WC–Co and 90MnCrV8 cold work tool steel. At the same time, Ag-based solders were also used to join cemented carbides by the means of laser brazing [7] and diffusion bonding [8]. The mechanical properties of the WC–Co/steel joints using Cu-based solders or Ag-based solders are well and seemingly meet the industrial demands. However, since cemented carbides are often used in corrosive environments [9], Cu-based solders and Ag-based solders are not the best choices for joining cemented carbides because of their poor corrosion resistance. Therefore, a new approach must be developed to improve the corrosion resistance of WC–Co/steel joints.

Recently, a functionally graded WC–Co/Ni composite (FGWC) was successfully fabricated [10]. In the FGWC, there are three sections, i.e., Ni layer, transitional layer and WC–Co substrate. Since Ni is considered a constructive intermediate material which has excellent plasticity and satisfactory corrosion resistance at high temperatures [11], the Ni layer of the FGWC is specifically designed to bond with steel and improve the corrosion resistance of the joints. On the other hand, diffusion bonding is an advanced solid-state joining technique, and by means of diffusion bonding, it is possible to bond the materials whose chemical and metallurgical properties are different [11]. Consequently, this paper aims to demonstrate the feasibility of diffusion bonding of the FGWC and steel. The microstructure and compositions of the joints are presented. The effect of bonding parameters (bonding temperature and holding time) on the tensile strength of the joints is also investigated in this paper.

Section snippets

Experimental procedure

Commercial WC, Co, and Ni powders were used as raw materials. The mixed WC–8 wt.%Co powders were ball milled in alcohol in stainless steel lined mills for 48 h, the milling speed were 56 rpm. After milling the pulp was dried and 1.1 wt.% synthetic rubber was added as a pressing aid. The WC–Co/Ni compacts were manufactured by pressing Ni powders with a pressure of 10 MPa onto pre-pressed WC–Co compacts within a rectangular die of 6.5 mm × 5.25 mm × 20 mm in size. By this method, a thin Ni layer with a

Results and discussion

The cross-section microstructure of the FGWC shown in Fig. 3a reveals that the Ni layer, transitional layer and WC–Co substrate are presented in the FGWC. Based on Fig. 3b and c, it is confirmed that the transitional layer is mainly comprised of WC and (Ni, Co), which leads to less stress-concentration at the interface of the Ni layer and the WC–Co substrate because of the gradient structure [13].

Fig. 4a exhibits the microstructure and areal distribution of elements of the FGWC/410ss joint. As

Conclusion

The diffusion bonding of the functionally graded WC–Co/Ni composite (FGWC) and 410 stainless steel (410ss) is successfully performed. The tensile strength of the joint increases firstly and then decreases with the bonding temperature or holding time increasing. The maximum tensile strength of the FGWC/410ss joints is 195 MPa bonded at 950 °C for 80 min, which is far higher than that of the WC–Co/410ss joints (58 MPa). In the FGWC/410ss joint, a diffusion layer is formed between the Ni layer and the

Acknowledgement

The authors thank Mrs. Hui Wang in Analytical & Testing Center at Sichuan University for assistance in the experiments.

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Short CommunicationInvestigation on diffusion bonding of functionally graded WC–Co/Ni composite and stainless steel

Abstract

Highlights

Introduction

Section snippets

Experimental procedure

Results and discussion

Conclusion

Acknowledgement

Acta Mater

Mater Des

Mater Des

Int J Refract Met Hard Mater

Int J Refract Met Hard Mater

Mater Des

Mater Charact

Int J Refract Met Hard Mater

Mater Lett

Mater Lett

Short Communication
Investigation on diffusion bonding of functionally graded WC–Co/Ni composite and stainless steel