Test device applied to coupled environment of stress, wear, and corrosion, and quantitative evaluation method

Abstract

This application relates to a test device applied to a coupled environment of stress, wear, and corrosion, and a quantitative evaluation method, and belongs to the field of failure analysis of materials. The test device includes a stress-loading mechanism configured to load a stress on a sample, a corrosion mechanism configured to conduct an electrochemical corrosion test on the sample, and a wear mechanism configured to wear a sample. The test device applied to a coupled environment of stress, wear, and corrosion of this application can establish a wear-stress-corrosion coupled action test process, and can investigate service behaviors of various metallic materials and metal matrix composites under conditions close to actual service conditions to obtain key behavior data under a multi-factor coupled action, quantitatively analyze a wear, a corrosion, a wear-corrosion interaction, a stress-wear interaction.

Claims

1. A test device applied to a coupled environment of stress, wear, and corrosion, comprising: a stress-loading mechanism configured to load a stress on a sample through a spring deformation, the stress-loading mechanism comprising: a support frame; a screw; a loading bolt, ends of the screw and the loading bolt being connected with the sample are each provide with a reserved groove, wherein a circular hole is reserved at each of two ends of the sample such that the two ends of the sample are inserted into reserved grooves of the screw and the loading bolt, respectively, and the sample is connected with the screw and the loading bolt through a pin; a loading nut; and a rectangular compression spring arranged between the support frame and the loading nut, where the rectangular compression spring is selected according to an applied stress and is deformed by tightening the loading nut; a corrosion mechanism configured to conduct an electrochemical corrosion test on the sample, the corrosion mechanism comprises a corrosion chamber, and an opening is formed at a top of the corrosion chamber to facilitate feeding of an electrolyte and a reciprocating movement of a friction component of a wear mechanism through the opening; and the wear mechanism configured to wear a sample through a friction wear testing machine.

2. The test device applied to a coupled environment of stress, wear, and corrosion according to claim 1, further comprising hexagonal holes are formed in the support frame, the screw and the loading nut have hexagonal shapes such that during installation, the screw and the loading bolt penetrate through the hexagonal holes to allow a fixed connection between an end of the support frame and the two ends of the sample.

3. The test device applied to a coupled environment of stress, wear, and corrosion according to claim 2, wherein in a chemical corrosion test process, except for a test surface, remaining surfaces of the sample are insulated and sealed with a rubber stopper; a through hole is formed at each of two sides of the corrosion chamber, and the rubber stopper is arranged in the through hole such that the two ends of the sample penetrate through rubber stoppers, respectively, and edges of the sample and the rubber stoppers are sealed with a sealant; reserved holes are formed in a side wall of the corrosion chamber to insert a reference electrode and a counter electrode; and a bottom of the corrosion chamber is provided with a gasket to reduce wear loads borne by two ends of the corrosion chamber, and a material of the gasket is an electrically non-conductive material and preferably a plastic.

4. The test device applied to a coupled environment of stress, wear, and corrosion according to claim 3, wherein the friction wear testing machine comprises: a grinding ball and clamping mechanism that further comprises a grinding ball; a spring collet, the grinding ball being arranged in the spring collet; and a sleeve, the grinding ball being fixed by tightening the sleeve; wherein the grinding ball is in contact with the sample, and is driven by a servo motor to move left and right in a reciprocating manner to wear the sample.

5. A quantitative evaluation method for the test device according to claim 1 as applied to a coupled environment of stress, wear, and corrosion comprising: winding each of two ends of a processed sample with an insulating tape for insulation, arranging the processed sample in a corrosion chamber; before installation, arranging a gasket under the sample, and sealing the two ends of the sample with rubber stoppers to avoid leakage of an electrolyte; inserting a reference electrode and a counter electrode into reserved holes in a side wall of the corrosion chamber; a screw and a loading bolt are fixed on a support frame; inserting the two ends of the sample into reserved grooves of the screw and the loading bolt, and fixing a rectangular compression spring and a loading nut on the loading bolt successively, and arranging and inserting a pin into circular holes reserved in the screw and the sample, a diameter of each circular hole is the same as a column diameter of the pin.

6. The quantitative evaluation method according to claim 5, comprising: (A) using a corrosive wear model to calculate a total material loss rate T.sub.W+C, a corrosion-free wear rate W.sub.0, a wear-free corrosion rate C.sub.0, an action W.sub.C of a corrosion on a wear rate, and an action C.sub.W of a wear on a corrosion rate during a wear corrosion; and (B) calculating a total material loss rate T.sub.S+W+C, an action T.sub.S of a stress on a wear corrosion, an action C.sub.S of the stress on a corrosion, and an action W.sub.S of the stress on a wear under a coupled action of stress, wear, and corrosion.

7. The quantitative evaluation method according to claim 6, wherein a wear-corrosion interaction in step (A) meets the following equation:
T.sub.W+C=W.sub.0+C.sub.0+C.sub.W+W.sub.C where $T_{W+C}=\frac{V_{W+C}}{\mathrm{At}}24365;W_0=\frac{V_0}{\mathrm{At}}24365;C_0=\frac{K_1{i}_{C}EW}{};C_W=C_{W+C}-C_0=\frac{K_1\left(i_{W+C}-i_C\right)EW}{};$ and
W.sub.C=T.sub.W+C(W.sub.0+C.sub.0+C.sub.W) wherein V.sub.W+C represents a surface wear volume during a corrosive wear, mm.sup.3; V.sub.0 represents a surface wear volume during a pure wear, mm.sup.3; A represents an area of a sample exposed to a corrosive liquid, mm.sup.2; t represents a time of a coupled action, h; K.sub.1 represents a constant of 3.2710.sup.3 mm.Math.g.Math.(A.Math.cm.Math.yr).sup.1; i.sub.C represents a corrosion current during a pure corrosion, A.Math.cm.sup.2; i.sub.W+C represents a corrosion current during a corrosive wear, A.Math.cm.sup.2; EW represents an equivalent mass of a sample; and p represents a density of a sample, g.Math.cm.sup.3; and if C.sub.W>0, it indicates that the wear has an accelerating action on the corrosion; if C.sub.W<0, it indicates that the wear has an inhibiting action on the corrosion; if W.sub.C>0, it indicates that the corrosion has an accelerating action on the wear; and if W.sub.C<0, it indicates that the corrosion has an inhibiting action on the wear.

8. The quantitative evaluation method according to claim 7, wherein a wear-corrosion interaction in the calculating a total material loss rate T.sub.S+W+C, meets the following equation:
T.sub.S+W+C=T.sub.W+C+T.sub.S where $T_{S+W+C}=\frac{V_{S+W+C}}{\mathrm{At}}24365;T_{W+C}=\frac{V_{W+C}}{\mathrm{At}}24365;\mathrm{and}$ and $T_S=T_{S+W+C}-T_{W+C}=\frac{V_{S+W+C}-V_{W+C}}{\mathrm{At}}24365$ the action T.sub.S of the stress on the wear corrosion is divided into an action C.sub.S of the stress on a wear and an action W.sub.S of the stress on a corrosion; $C_S=C_{S+W+C}-C_{W+C}=\frac{K_1\left(i_{S+W+C}-i_{W+C}\right)EW}{};$ and
W.sub.S=T.sub.SC.sub.S wherein V.sub.S+W+C represents a surface wear volume under the coupled action of stress, wear, and corrosion, mm.sup.3; and i.sub.S+W+C represents a corrosion current under the coupled action of stress, wear, and corrosion, A.Math.cm.sup.2; and if C.sub.S>0, it indicates that the stress has an accelerating action on the corrosion; if C.sub.S<0, it indicates that the stress has an inhibiting action on the corrosion; if W.sub.S>0, it indicates that the stress has an accelerating action on the wear; and if W.sub.S<0, it indicates that the stress has an inhibiting action on the wear.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompany drawings of the specification constituting a part of the present application provide further understanding of the present application. The schematic embodiments of the present application and description thereof are intended to be illustrative of the present application and do not constitute an undue limitation of the present application.

(2) FIG. 1 is a partial cross-sectional view of the test device applied to a coupled environment of stress, wear, and corrosion in the present disclosure;

(3) FIG. 2 is a top view of the test device applied to a coupled environment of stress, wear, and corrosion in the present disclosure;

(4) FIG. 3 shows potentiodynamic polarization curves and corrosion current densities of a titanium alloy sample in the three environments of corrosion, corrosion-wear, and corrosion-wear-stress, where FIG. 3A shows the potentiodynamic polarization curves and FIG. 3B shows the corrosion current densities; and

(5) FIG. 4 shows wear volumes of a titanium alloy sample in the three environments of corrosion, corrosion-wear, and corrosion-wear-stress.

(6) In the figures, 1: a support frame; 2: a screw; 3: a pin; 4: a corrosion chamber; 5: a reference electrode; 6: a grinding ball and clamping mechanism; 7: a counter electrode; 8: a rectangular compression spring; 9: a loading nut; 10: a loading bolt; 11: a rubber stopper; 12: a gasket; 13: a sample, 14: circular hole and 15: reserved groove.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(7) In order to make those skilled in the art well understand the technical solutions in the specification, the technical solutions in the embodiments of the specification are clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the specification, but are not limited thereto. Those not described in detail in the present disclosure are the conventional techniques in the art.

Example 1

(8) A test device applied to a coupled environment of stress, wear, and corrosion is provided. As shown in FIG. 1 and FIG. 2, the test device includes a stress-loading mechanism configured to load a stress on a sample, a corrosion mechanism configured to conduct an electrochemical corrosion test on the sample, and a wear mechanism configured to wear a sample. The stress-loading mechanism is configured to load the stress on the sample through a spring deformation. The corrosion mechanism includes a corrosion chamber 4. An opening is formed at a top of the corrosion chamber 4 to facilitate feeding of an electrolyte through the opening and a reciprocating movement of a friction component of the wear mechanism, and a corrosion environment can be changed by adjusting a Cl-concentration and a pH in the electrolyte. The wear mechanism is configured to wear the sample through a friction wear testing machine. Different wear loads and wear frequencies are applied by the friction wear testing machine. A material can be any metallic material or metal matrix composite.

(9) The stress-loading mechanism includes a support frame 1, a screw 2, a loading bolt 10, a loading nut 9, and a rectangular compression spring 8. Ends of the screw 2 and the loading bolt 9 to be connected with the sample 13 each are provided with a reserved groove 15. A circular hole 14 is reserved at each of two ends of the sample. The two ends of the sample are inserted into reserved grooves 15 of the screw 2 and the loading bolt 10, respectively, and the sample is connected with the screw and the loading bolt through a pin 3.

(10) The rectangular compression spring 8 is arranged between the support frame 1 and the loading nut 9. A specification of the rectangular compression spring is selected according to an applied stress. The rectangular compression spring 8 is deformed by tightening the loading nut 9. A deformation amount is measured according to a displacement distance of the loading nut, and a loaded stress value can be determined according to a Hooke's law.

(11) In order to ensure that a sample does not twist during a stress loading process, the loading bolt and the loading nut are processed into hexagonal shapes. Hexagonal holes are formed in the support frame 1. During installation, the screw 2 and the loading bolt 10 penetrate through the hexagonal holes to allow a fixed connection between an end of the support frame and the two ends of the sample.

(12) In a chemical corrosion test process, except for a test surface, remaining surfaces of the sample are insulated and sealed with a rubber stopper 11. A through hole is formed at each of two sides of the corrosion chamber 4, and the rubber stopper 11 is arranged in the through hole. A cuboid is cut out inside each rubber stopper 11 to facilitate the two ends of the sample to penetrate through rubber stoppers, respectively, and edges of the sample and the rubber stoppers are sealed with a sealant.

(13) Reserved holes are formed in a side wall of the corrosion chamber 4 to insert a reference electrode 5 and a counter electrode 7. The test device of the present disclosure is implemented through a three-electrode system, including a working electrode (the sample itself), the reference electrode, and the counter electrode (an auxiliary electrode).

(14) A bottom of the corrosion chamber 4 is provided with a gasket 12 having an appropriate height to guarantee a normal wear process and reduce wear loads borne by two ends of the corrosion chamber. A material of the gasket 12 is an electrically non-conductive material and preferably a plastic.

(15) Further preferably, the friction wear testing machine includes a grinding ball and clamping mechanism 6. The grinding ball and clamping mechanism includes a grinding ball, a spring collet (an ER collet), and a sleeve. The grinding ball is arranged in the spring collet. The grinding ball is fixed by tightening the sleeve. The grinding ball is in contact with the sample, and is driven by a servo motor to move left and right in a reciprocating manner to wear the sample.

(16) Further preferably, a plurality of and preferably three test devices are arranged to facilitate controlled experiments.

(17) Further preferably, a working process of the test device is as follows:

(18) Two ends of a processed sample 13 each are wound with an insulating tape for insulation, and then are arranged in the corrosion chamber 4. Before the installation, the gasket 12 is arranged under the sample, and the two ends of the sample are sealed with the rubber stoppers 11 to avoid leakage of the electrolyte. The reference electrode 5 and the counter electrode 7 are inserted into the reserved holes in the side wall of the corrosion chamber 4. The screw 2 and the loading bolt 9 are fixed on the support frame 1. The two ends of the sample are inserted into the reserved grooves 15 of the screw and the loading bolt. The rectangular compression spring 8 and the loading nut 9 are fixed on the loading bolt 10 successively. The cylindrical pin 3 is arranged and inserted into circular holes 14 reserved in the screw and the sample. A diameter of each circular hole 14 is the same as a column diameter of the pin.

(19) The three test devices have a same working principle. The three test devices are arranged to implement controlled experiments, and the controlled experiments are conducted successively. The reference electrode and the counter electrode are arranged in the corrosion chambers of the three test devices successively, and a prepared corrosive liquid is injected into the corrosion chambers successively. A wear load and a wear frequency are set for the friction wear testing machine. The grinding ball (a spherical Si.sub.3N.sub.4 ceramic ball) is allowed through the friction wear testing machine to move downward to contact the sample, and a load in a downward direction is applied. Relative reciprocating sliding between the grinding ball and the sample allows a wear. As a result, the sample is subjected to a stress action caused by the loading bolt, a corrosion action caused by an environmental medium in the corrosion chamber, and a wearing action caused by reciprocating sliding of the grinding ball, and a damage is caused by a coupled action of stress, wear, and corrosion to the sample.

Example 2

(20) A quantitative evaluation method of a test device applied to a coupled environment of stress, wear, and corrosion is provided. In this example, a device and method for testing a failure behavior of a titanium matrix composite (Ti6Al4V+2BN produced by laser additive manufacturing) under a multi-factor coupled action (stress-wear-corrosion) is provided. The test device includes a stress-loading mechanism configured to load a stress on a sample, a corrosion mechanism configured to conduct an electrochemical corrosion test on the sample, and a wear mechanism configured to wear a sample.

(21) In this example, a constant load of 300 MPa was applied to a titanium alloy sample for 20 d, a 30 N wear load was applied with a wear frequency of 1 Hz and a sliding distance of 4 mm, and a corrosion environment was 3.5 wt. % NaCl. An exposed area of the sample was 6 mm.sup.2. A test was conducted for 0.5 h at room temperature. The test device was assembled according to Example 1.

(22) During a test process, with an electrochemical workstation, corrosion currents i.sub.C, i.sub.W+C, and i.sub.S+W+C under a corrosion action, a wear-corrosion coupled action, and a coupled action of stress, wear, and corrosion were recorded. Potentiodynamic polarization curves and corrosion current densities were shown in FIG. 3. After the test was completed, the sample was taken out from the corrosion environment and tested by a three-dimensional morphology analyzer for surface wear volumes V.sub.0, V.sub.W+C, and V.sub.S+W+C (as shown in FIG. 4). i.sub.C, i.sub.W+C, i.sub.S+W+C, V.sub.0, V.sub.W+C, V.sub.S+W+C, K.sub.1 (3.2710.sup.3 mm g (A.Math.cm.Math.yr).sup.1), EW (11.98), and (4.89 g.Math.cm.sup.3) were substituted into the following equations to quantitatively analyze a wear rate W.sub.0, a corrosion rate C.sub.0, an action W.sub.C of a corrosion on a wear rate, an action C.sub.W of a wear on a corrosion rate, an action C.sub.S of a stress on a corrosion rate, and an action W.sub.S of a stress on a wear rate:

(23) $W_0=\frac{V_0}{\mathrm{At}}24365=\frac{0.300174}{60.5}24365=876.508\mathrm{mm}.Math.{\mathrm{yr}}^{-1}=876508\mathrm{.Math.m}.Math.{\mathrm{yr}}^{-1};$$T_{W+C}=\frac{V_{W+C}}{\mathrm{At}}24365=\frac{0.3002}{60.5}24365=876.584\mathrm{mm}.Math.{\mathrm{yr}}^{-1}=876584\mathrm{.Math.m}.Math.{\mathrm{yr}}^{-1};$$T_{S+W+C}=\frac{V_{S+W+C}}{\mathrm{At}}24365=\frac{0.298248}{60.5}24365=870.884\mathrm{mm}.Math.{\mathrm{yr}}^{-1}=870884\mathrm{.Math.m}.Math.{\mathrm{yr}}^{-1};$$C_0=\frac{K_1{i}_{C}EW}{}=\frac{0.003270.0251211.98}{4.89}=0.0002\mathrm{mm}.Math.{\mathrm{yr}}^{-1}=0.2\mathrm{.Math.m}.Math.{\mathrm{yr}}^{-1};$$C_W=C_{W+C}-C_0=\frac{K_1\left(i_{W+C}-i_C\right)EW}{}=\frac{0.00327\left(6.33506-0.02512\right)11.98}{4.89}=0.050549\mathrm{mm}.Math.{\mathrm{yr}}^{-1}=50.55\mathrm{.Math.m}.Math.{\mathrm{yr}}^{-1};$$W_C=T_{W+C}-\left(W_0+C_0+C_W\right)=876584-\left(876508+0.20+50.55\right)=25.25\mathrm{.Math.m}.Math.{\mathrm{yr}}^{-1};$$T_S=T_{S+W+C}-T_{W:C}=870884-876584=-5700\mathrm{.Math.m}.Math.{\mathrm{yr}}^{-1};$$C_S=C_{S+W+C}-C_{W+C}=\frac{K_1\left(i_{S+W+C}-i_{W+C}\right)EW}{}=\frac{0.00327\left(19.97727-6.33506\right)11.98}{4.89}=0.10929\mathrm{mm}.Math.{\mathrm{yr}}^{-1}=109.29\mathrm{.Math.m}.Math.{\mathrm{yr}}^{-1};\mathrm{and}$$W_S=T_S-C_S=-5700-109.29=-5809.29\mathrm{.Math.m}.Math.{\mathrm{yr}}^{-1}.$

(24) The above results indicate that the wear has an accelerating action on the corrosion and the corrosion has an accelerating action on the wear; and the stress has an accelerating action on the corrosion and the stress has an inhibiting action on the wear.

(25) The above are preferred implementations of the present disclosure. It should be noted that a person of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present disclosure, but such improvements and modifications should also be deemed as falling within the protection scope of the present disclosure.